AP42 Section:

Reference:

Title:

11.25

Clays,

S. H. Patterson and H. H. Murray,

Industrial Minerals And Rocks, Volume 1, Society Of Mining Engineers, New York, 1983.

~

The term clay is somewhat ambiguous un- less specifically defined, because it is used in three ways: ( I ) as a diverse group of fine- grained minerals, (2) a5 a rock term, and (3) as a particle-size term. Actually, most persons using the term clay realize that it has several meanings, and in most instances they define it. As a rock term, clay is difficult to define be- cause of the wide variety of materials that com- , m e it; therefore, the definition must be gen- 'eral. Clay is a natural earthy, fine-grained ma- Iterial composed largely of a group of crystalline ;minerals known as the clay minerals. These minerals are hydrous silicates composed mainly of silica, alumina, and water. Several of these minerals also contain appreciable quantities of iron, alkalies, and alkaline earths. Many defini- tions state that a clay is plastic when wet. Most clay materials do have this property, but some clays are not plastic; for exaniple, halloysite and flint clay.

As a particle-size term, clay is used for the category that includes the smallest particles. The maximum-size particles in the clay-size grade are defined differently on various grade scales. Soil imestigators and mineralogists gen- erally use 2 micrometers as the maximum size, whereas the widely used scale by Wentworth (1922) defines clay as material finer than a p proximately 4 micrometers.

Some authorities find it convenient to'use the term clay'for any fine-grained, natural, earthy, argillaceous material (Grim. 1968). When used this way, the term includes clay, shale,. or .ar- gillite, and some argillaceous soils.

: * Publication authorized by the Director. US Geological Survey. For other Acknowledgments. see pp. 642-643.

t US Geological Survey, Reston. VA. $Georgia Kaolin Co.. Elizabeth, NJ: pres-

ently, Dept. of Geology, Indiana University, Bloomington, IN.

: . ' ,

i I

i

!

. ~- . 586 Industrial Minerals and Rocks

Bentonite 4,467,605 88.425.737 . 4i422.075 106,528.550 4,184,619 115,234,996 Fuller's earth 1,529,619 73,430,515 1.568247 81,761.964 1,533,803 79,724.017 , Kaolin 6,973,314 367.782.408 7,760,600 462,320,088 7,878,993 527,098.w9

893,624 26,844,126 Ball clay 936,251 21,549,559 987,012 26,119,965 Fire clayt 3,125,953 42,561,432 2,932,343 47,178.993 2,095,361 36,022,134 Miscellaneous : '. i

clay 40,074,738 124,068,443 37278.803 122,735.1 17 32,494,837 114,700,246

Total* 57,107,430 717,818,034 54,949,080 846,644,677 49.081237 899.624.128 ' - _ I Source: Ampian. 1980: Ampian and Polk, 1981. .'"+ ; . ,

~

- -~ Definitions of classes of clay listed are given in the appropriate places in the text. t Fire clay is used with essentially the same meaning as refractory clay in this chapter. Fire clay is also the

only type of clay having a sharply declining production in recent years. This is due mainly to the method of reporting, in which some types of fire clay used for other than refractory products are now classified a i miscellaneous clay, and to the increasing use of higher quality and more durable refractory materials. tlncludes Puerto Rico. . ~ . . . .. . . ',

fuller's earth is actually bentonite. The over- lapping of the two terms is particularly evident where both bentonite and nonbentonite fuller's earth are used for the same purposes or prod- ucts, such as in drilling muds, bleaching or clarifying fats and oils, and carriers for insecti- cides and fertilizers. Kaolin. ball clay, halloysite, and refractory clays are grouped together be- cause they consist mainly of minerals of the kaolin group. Miscellaneous clay and shale is a grouping of several fine-grained materials of the type referred to as common clay in some reports.

The scientific and technological publications pertaining to clays are so numerous that to cover all the material in the format used for other chapters would require a book. Therefore, the authors have attempted to .summarize the subject matter and wherever possible have indi- cated by bibliographic reference where more detailed information is available. For example, the reference to Bicker (1970) is to a bulletin containing only brief summary information on the. economic geology of bentonite in Missis- sippi, but that bulletin contains references to virtually all published reports on bentonite in that state. :

The remaining parts of this introduction will be mainly an outline of some of the major ad- vancements in the broad field of clays since the 4th edition of Industrial Minerals and Rocks (Patterson and Murray, 1975) and acknowl- edgment to those who have helped in preparing this chapter. Our intent is to note where some

of the contributions, mainly in clay mineralogy. have been made, so that those who are inter- ested can find detailed information not included in this report.

A vast amount of new information on the mineralogy, geology, and technology of Clays has become available in recent years. One Of the principal sources is The Clay Minerals s03- ety. This professional and scientific society organized in 1963 from an informal group sponsored and partially supported for the PIC- ceding years by the National Academy of %I- ences-National Research Council. For five Yea? after that date, the papers presented at the SWt- ety's annual meetings were published in YOI-

umes by Pergamon Press. Since 1968, The Clay Minerals Society has published its own journal under the title Cloys and Clay Minerals. A second major source of information on clays, the publications of the Association In tep t lw nale pour I'Ptude des Argiles (AIPEA); t h y publications are principally volumes containlnB the papers presented at the triennial meetlnt7 of the association. A third e.yellent source Of information on clays is Clay Minerals, the jour- nal of The Clay Minerals Group of The Miner- alogical Society (London). In addition. Clay minerals groups or societies in France, Spain* Italy, Japan, Argentina, West Germany. and other countries have periodic publications. Con- siderable information on kaolin resources i" several countries is available in three vOlumn resulting from a symposium held at the Inter national Geological Congress in Czechoslovak'a

..

in 19t -1969~

on ka Confe ratosa

Sev umes few yq with r a b y Miner (Lon< includ therm one c StrUCtl (1961 invest volum erals I and \i of Thf (1970 tion o chemii Olphe lished fractic volum geolog in cer shaw yolum one. b lated I cia1 P: by We erable relate1 Anoth (1973 of cla formu

A g technc lished geolog agenci Of thi Part 3 here; impor the fo

Ma ous cl these I advan

..

._

Clays

Value I - 158234.996 79,724,017

26,844,126 527.098.6og

36,022,134 -.

114,700,246

899,624.128 - -

lay is also the :o_the method N CEfsiiird as .Y materials.

.. - ? mineralogy. ho are inter. not includcd

ation on thc ogy of clays :an. One 0 1 Iinerals Soci- c society wa, ormal. group for the pre.

demy of Sc-- For five years d at the soci- !shed in YOI- 168, The Cia!. own journal

Minerals. A in on clays is ,n Internatio- [PEA); therc es containinE oial meeting, ent source d rals, the jour. ,f The Miner. Iddition, C h !

rance, Spain. wmany. 3nd ications. Con- resources In

hree vo~umt' at the Inter-

zechoslovakia

in 1968 (Malkovskj. and Vachtl, 1969a, 1969b, 1 9 6 9 ~ ) and in the report of another symposium on kaolin held at the 1972 International Clay

Several major textbooks and reference vol- umes on clays have been published in the last few years. They include one concerned mainly with mineralogy and another on applied miner- alogy of clays by Grim (1962, 1968). The Clay Minerals Group of the Mineralogical Society (London) has a classic series on clay minerals,

including a. volume concerned with differential thermal analysis, edited by Mackenzie (1957), one on the X-ray identification and crystal structures of clay minerals edited by Brown (1961). and a third on the electron-optical investigation of clays edited by Gard (1971). A volume on the electron microscopy of clay min- erals has also been prepared by Beutelspacher and Van Der Marel (1968). A Special Paper of The Geological Society of America by Carroll

tion of clays. An excellent volume on colloid chemistry of clays has been authored by Van

1. In 1967, Zvyagin (1967) pub- lished a book concerned with the electron dif-

sis of clays. Gillott's (1968)

geology. Recent volumes concerning clays used in ceramic materials include books by Grim- . shaw (1972) and Clews (1969). An excellent

volume on the geology and origin of clays is one by Millot (1964), which has been trans- lated'frpm French into English. A recent Spei';. cia1 Paper of The Geological Society of America

-by Weaver and others (1972) contains consid- erable information on the geochemistry of clays related to diagenesis and metamorphism. Another recent volume by Weaver and Pollard (1973) contains information on the chemistry

'. A great deal of information on the geology, technology, and uses of clay-has also been pub- lished by various provincial, state, and federal

.of the major reports are listed by Hoy in -Part 3 of Volume 1 and will not be repeated

here; however, reference to some of the more

ing sections of this chapter,

new uses, shifts in demand, and increases in both domestic and export markets. The chang- ing conditions, particularly increasing freight rates, the energy crisis, other production and marketing costs, and the pressures brought about by governmental controls and mining laws resulting from requirements and restric- tions related to environmental considerations, etc., have motivated the formation of organiza- tions to look after the interests of some of the clay-producing industries. One of these organi- zations formed recently is the Absorptive Min- erals Institute, having headquarters at No. 1 Illinois Center, 1 I 1 E. Wacker Drive, Chicago, 1L 60601. This institute was formed mainly to represent the producers of absorbent granules and other fuller's earth products. A similar organization, the Bentonite Producers Associa- tion, was organized in 1971 in Casper, WY, and represents the interests of the producers of bentonite. The kaolin industry organized the US Clay Producers Traffic Association which was incorporated in 1953 in New Jersey. In addition to these organizations dealing specifi- cally with clays, the clay industry and other mining industries formed mining associations in many states, including Georgia and Texas in 1972, in order to protect their interests against restrictive state and federal legislation.

Bentonite and Fuller's Earth

Definitions and Classifications

The term bentonire was first proposed in 1898 by Knight (1898), a year after he had named this clay taylorite; taylorite was found to be preoccupied. The name taylorite was after the Taylor ranch, the site of the first mine, near Rock River, WY, and the name bentonite is from the Benton Shale in which the clay was thought at that time to occur. The Benton Shale was, in tum;named after Fort Benton, MT, located more than 400 miles north of Rock River.

Early in the 20th century, several geologists recognized that bentonite, mainly in beds in Cretaceous and Tertiary rocks, originated from transported volcanic materials. This recogni- tion led to definitions based on origin, the one most widely quoted and generally accepted by geologists is the following definition by Ross

-.

and Shannon (1926): . .

Bentonite is a rock composed essentially '"

of a crystalline clay-like mineral formed by devitrification and the accompanying chemi- . cal alteration of a glassy igneous material,

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. . _..- .. swell moderately and to form gel, of lesser'vol. i umes than equal masses of the sodium type. .$ Bentonite, because of the general relationshipof : swelling and exchangeable ion characteristics. h 1 ; commonly divided into the high-swelling or ., sodium, low-swelling or calcium, and moderate. swelling or intermediate types. The term sub- - bentonite (Davis, Vacher, and Conley, 1940) . t

is used inconsistently in industry for the low or moderate-swelling varieties. The authors believe the use of this term should be discouraged be- cause of its implication of a low quality or low

usually il tuff or volcanic ash; and it often contains variable proportions of accessory crystal grains that were originally pheno- crysls in the volcanic glass. These are feld- spar (commonly orthoclase and oligoclase), biotite, quartz, pyroxenes, ziicon and vari- ous other minerals typical of volcanic rocks. The characteristic clay-like mineral has a micaceous habit and facile cleavage. high birefringence and a texture inherited from volcanic tuff or ash. and it is usuallv the mineral montmorillonite, but less often beidelite.

' The difficulty in applying the foregoing defi- nition to bentonite as an industrial mineral com- modity is that it is based on origin and is restrictive to an ash, tuff, or volcanic glass parent material. Therefore, bedded deposits consisting of the clay minerals required by this definition but having uncertain origin or.parent materials cannot properly be called bentonite. Furthermore, many deposits in the western: United States and in other countries that have formed from rocks other than the types re- quired by the definition are being mined and sold as bentonite.

Perhaps the best definition of bentonite as an industrial mineral is one given by R. E. Grim in a plenary lecture at the International Clay Con- ference (AIPEA) at Madrid, Spain, June 27, 1972. According to this redefinition, which will be used in this chapter, bentonite is a clay con- sisting essentially of smectite minerals (mont- morillonite group of some usages), regardless of origin or occurrence. This definition solves the problem of the difference between the geologic and industrial usages of the term and overcomes the difficulty in assigning a name to smectite clay that formed from igneous rock other than ash, tuff, or glass, o r those of sedimentary or uncertain origin. However, bentonite, when used with this meaning is stal a rock term (con- sisting of more than one mineral), and it will not be possible to distinguish it from fuller's earth in many instances.

One way of classifying bentonite is based on its swelling capacities when wet or added to water. Bentonite having sodium (Na') as either the dominant or as an abundant exchangeable ion typically has very high swelling capacities and forms gel-like masses when added to water. Bentonite in which exchangeable calcium (Ca++) is more abundant than other ions has much lower swelling capacities than sodium varieties. Some calcium types swell little more than com- mon clay, and most crumble into granular masses in water. Intermediate calcium-sodium bentonites, the so-called mixed types, tend to

value and the lack of a mineralogical or u x ' , 1 basis for it. -+;::,:t!5.. -__ i

In the United States bentonite is also classi- fied by geographic location and the uses for which it is sold. Inasmuch as most of the low- swelling calcium type occurs in states bordering the Gulf of Mexico, this variety is commonly called Southern bentonite. The largest-high- swelling sodium bentonite deposits and the major producing districts are in-Wyoming and adjacent states. Therefore, this bentonite is commonly called Wyoming or Wertern type. Such terms as drilling mud bentonite, foundry bond bentonite, and taconite bond bentonite relating directly to use are applied in marketing. Other terms including high and low-yield ben- tonite, high and low-gel bentonite, and high and low-strength bentonite are also used to dis- tinguish different grades.

The varied classifications notwithstanding. bentonite occurs in so many different varieties that some cannot logically be classified accord- ing to any of the foregoing groupings. One of these types is hectorite, which is a high-swelling lithium-bearing variety of smectite occurring mainly in California and adjacent states. It is, therefore, not a Wyoming type, and it occur3 even farther west than the so-called westem bentonites. Others are bentonites having mag- nesium (Mg'+) or hydrogen (H-) as the most abundant or dominant exchangeable ion. These types are neither sodium nor calcium varieties, and apparently some are low swelling, whereas others have rather high-swelling capacities.

Still another type of bentonite, the so-called potassium type, K-bentonite, 6r metatientonite. occurs in Ordovician and other Paleozoic rock: at many places in Appalachian and MissiisiPPl Valley regions and elsewhere. This bentonite, which is generally thought to have formed from volcanic ash, consists mainly of illite and mixed- layer minerals. Smectite minerals are ordinarjlY present in only minor quantities. Because of 11s

mineral composition, this bentonite contains a P preciably more potassium than most other types.

The I this t morp attem was v Dayti bento sleeve

Th catch mater and c or m term plied wool, from centu fullin, purif] the te this u!

Ex> mine, the vi the g earth, troleu mean for th majoi howe many sorbei the pi certai absorl modif Thl

ler's e havin. meani sense. nafur. clays altere called 1972' ing e, activc activ;: active the t there! ing i:

clay i

type 1

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- . .. .*. -i-*;-ILi' - .. . i . _.. <i . ., .. .. , _ ....... ..

The meta prefix originates from the idea that this bentonite was altered by low-grade meta- morphism or diagenesis. Apparently, the only attempt to use K-bentonite in the United States was when five or six carloads were mined near Dayton, Rhea County, TN, about 1928; this bentonite was used for purifying lard (Gilder- sleeve, 1946), and no further mention of this

The term fuller’s earth is more or less a .i catchall for clay or other fine-grained earthy 1 -material suitable for bleaching and absorbent

and certain other uses: It has m compositional . . or mineralogical meaning. The origin of the

term dates hack into antiquity; it wa-. first ap- plied to material used in cleansing and fulling

- wool, thereby removing the lanolin and dirt ~. from it. When in the latter half of the last

‘century it was found that some earths used for fulling would also serve in decolorizing and

. purifying mineral, vegetable,^ and animal oils, .!the term fuller’s earth was modified to include : this usage. ’

Extensive use of fuller’s earth in processing 1. mineral oils in the first half of this century and

the virtual end of its use in fulling fiber led to -‘the general application of the term, fuller’s

type will he made. . .

”-

z

earth, as meaning primarily earth used in pe- troleum processing. Further modification of the meaning came about as other uses develoned for theiar th and replaced oil processing as-the major use. The term fuller’s earth is retained. however, for fine-grained materials used fo; many purposes.~Most of these uses require ah- sorbent properties.in one form or another, hut the properties required for some uses, such as

. certain drilling muds and fillers, are other than

. absorbency and, therefore, result in further _ _ modification of the term. -. E. The classification and understanding of ful- ’. ler’s earth are also comulicated hv several terms I’ i: having more or less duplicate or overlapping : meanings. When applied in the oil-processing - sense, fuller’s earth has the same meaning as

<unaturally active clay. Fuller’s earth and other 1 clays which are treated with acid or otherwise $.altered to improve their desirable properties are .-called ._ activated clay (Torok and Thompson, ‘-1972). The terms bleaching clay and bleach- k%g earth are applied mainly to both naturally >% ;active and activated clay, hut they also include ;.activated bauxite (Rich, 1960). Both naturally *active and activated clays are included under -the term absorbent clays (Nutting, 1943); $!hefefore, this term has nearly the same mean- &:mg as bleaching clay: The term absorbent &lay is applied to fuller’s earth used for a wide

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:m-

_ _ .. .. . -

variety of absorbing purposes which are differ- ent from that of processing oils.

History and Use Bentonite: Bentonite mining began on the

Taylor ranch near Rock River, WY, in 1888. This bentonite reportedly was shipped crude to Philadelphia where it sold for $25 a ton and was used in making cosmetics, A mine was opened in the Upton, WY, district on the western side of the Black Hills in 1903. The early method of drying was to rake the bentonite by hand over steel plates heated by wood or coal fires.

The date of the fint mining of southern bentonite is somewhat conjectural because of the confusion between the terms bentonite and fuller’s earth. One fuller’s earth deposit near Gonzales, Texas, that is almost certainly bento- nite was mined as early as 1906, and another deposit in that same state mined during the Civil War (Lang et al., 1940) may also have been bentonite. Large-scale mining of calcium-type . bentonite began in Mississippi in the early 1930s (Bicker, 1970), and bentonite deposits were used as fuller’s earth in several states about this time.

The value of bentonite as foundry-sand bond was recognized in the 1920s. and the iron and steel foundries have since been major consum- ers of bentonite. Bentonite was first used as drilling mud in the late 1920s or early 1930s, a n d bentonite is still one of the most efficient materials for drilling muds where the rocks penetrated contain only fresh water. The high- swelling Wyoming bentonite is the most efficient type for drilling mud, hut the high-viscosity properties of hectorite make it useful in muds (Larsen, 1955). Some Texas bentonite is also used for drilling muds, particularly in shallow wells, and commonly it is treated with soda ash, polymers, or other chemicals to make it suitable for this use. Low-quality bentonite when sold for use in drilling mud is commonly classified merely as clay rather than bentonite (Anon., 1972d).

Bentonite production remained small during the first few decades of mining, and the first yearly total sufficiently large to he separated from miscellaneous clays in the U S Bureau of Mines statistics was in 1930 when production was only a few thousand tons. Demands for bentonite increased during World War 11, hut a yearly total of 1 million tons was not reached until 1950. More than 2 million tons was pro- duced in 1966, and the peak production year to date was 1978, when 4,467,605 tons were sold or used by producers. Bleaching clay (oil

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-~ Industrial Minerals and Rocks

u) c 0 c .- 0‘ .c u)

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4,500

4,000

3,500

3,000

2,500

2,000

I .500

I,O00

500

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1965 1967 1969 1971 1973 1975 1977 1979 1981~ YEAR .. -

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. . - . FIG. I-Benfonife sold or used by domestic producers for specified uses

(Ampian, 1980, 1983). i ,

refining, filtering, clarifying, and decolorizing), drilling mud, iron-ore pelletizing, and foundry- sand bonding have been the major uses of bentonite since World War II (Fig. I ) . Begin- ning about 1950, steel companies used Wyn- ming-type bentonite as a bond for pelletized

: taconite ore. This use grew rapidly, and in recent years approximately one-third of the na- tional production has been used for this pur- pose.

In addition to the major uses, bentonite is used in’many miscellaneous products. and hun- dreds of patents for speciality uses have been issued or applied for. The speciality uses in- clude filtering agents (one of which is a high- value product for clarifying wine, and another is a less costly one for treating waste water), water impedance (preventing seepage loss from reservoirs, irrigation ditches, and waste-disposal ponds, and seepage through basement walls. tunnel walls, and other structures), ingredients in cosmetics, animal feed, pharmaceuticals, col-

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. . loidal fillers for certain types of paints, an addi- tive tn ceramic raw materials to increaz plasticity, fire-retarding materials, and for many other purposes (Papin, 1964). The white ben. tonites occurring in Texas and Nevada and im- ported from Italy are ,particularly suitable for many of the speciality products, and a great deal of research evaluating them for many Uses has been done. One of the unique uses of h@ swelling bentonite that is likely to increase iS In the “slurry trench’ or “diaphragm wall” method nf.excavation in construction in are>s of uncon- solidated rock or soil (Blackman, 1969; La!%* 1971). In this method, the trench or hole being excavated is filled with bentonite slurry and the earth being excavated is removed through it., A thin filter cake on the walls of the excavatlOn prevents loss of fluid, and the hydrostatic head of the slurry prevents caving and running of loore soils, which makes costly shoring unnecev sary. Considerable quantities of bentonite were Once used in making catalysts for petroleum re-

fining, but t lysts in the War 11. HO have been p clays in lap where in rec is used foi multiplecol

Fuller’s I confusing a earth in tht fuller’s eart I893 near C Co. (prede White Ow: brick from, was not st

Alsatian im recognized mined in G velopment years later : ing mineral on a small (Miser, 19 fining of co

.Both of lated to thc oils and fai poses. Cla: undoubted1 Europe in Little effor records an< that soldie: used Woo skins durii Smock, 1: an iron-ol mined in t fuller’s ea used to t (Lang et were rep0 ing blanke cleansing period.

The use continued The dema mineral oi this centu mately 31 of the tc year. The purpose I cially whe

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an addi. increosc or man! lite hcn. and im- able for a grcal

my use, of high- ase is in method uncon.

t ; Lans. ,le beinE and the $hit. A :avatirrn tic head ning 01 inneccr. ite werr eum IC-

fining, but the market for these types of cata- lysts in the United States declined after World War 11. However, sizable quantities of catalysts have been produced from bentonite and similar clays in Japan, the United Kingdom, and else- where in recent years. Acid-activated bentonite is used for bleaching oils and in making . multiplecopy paper requiring no carbon paper.

z~ Fuller’s Earth: Published reports give rather confusing accounts of the discovery of fuller’s

. earth in the United States. Several.state that . fuller’s earth was discovered in this country in . 1893 near Quincy, FL, by the Owl Commercial ? Co. (predecessor of the present makers of - .. White Owl cigars) during an attempt to burn :’. brick from clays on tobacco property. ‘The clay “r was not suitable for making brick, hut an - Alsatian immigrant employed as a farm worker 2 recognized that it was similar to fuller’s earth :.. mined in Germany. His observation led to de- * velopment of the first mine near Quincy two I- ,years later and to the use of this clay in process- ? iog mineral oils. Fuller’s earth had been mined . on a small scale, however, in Arkansas in 1891 7 (Miser, 1913), and tested for use in the re-

fining of cottonseed oil. -. Both of these reported discoveries are re-

lated to the use of fuller’s earth in processing . oils and fail to note its earlier use for other pur-

poses. Clays and other earthy materials were . undoubtedly used by the early settlers from __ Europe in cleansing wool and other materials. Little effort was made to search the historical

c. records and to document this, but it was found : that soldiers stationed near Perth Amboy, Nl, .. used Woodbridge fire clay for cleansing buck- :. skins during the Revolutionary War (Cook and .- Smock, 1878). Fuller’s, earth associated with 7 an iron-ore bed near Kent, CT, had been ,. mined in the early 1800s (Silliman, 1820j, and = fuller’s earth near Falls City, Texas, had been ’ used to bleach sugar during the Civil War 8 (Lang et al., 1940). Also, American Indians s, were reported to have used bentonite in clean- “-ing blankets, and they probably dug it for other

cleansing purposes before the Columbian ?‘period. i;.

$ The use of fuller’s earth in the refining of oils ;. continued to he the major one for many years. $.The demand. for fuller’s earth for processing !$ mineral oil increased rapidly in the first part of y this century and reached, a peak of approxi- Ymately 317,000 tons in 1930: this was 91.1% 5 of the total United States production that ;.,year. The production of fuller’s earth for this &’ purpose began to decrease thereafter, espe- L . k..Cially when activated bauxite was introduced in

5

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1937 and magnesium silicate in 1940 as more efficient substitutes. The market for this use was also depressed by improvements in refining methods, which produce oils requiring little purification or bleaching. In recent years, the production of fuller’s earth for use in refining mineral oils has maintained a rather uniform rate of 35,000 to 40,000 tpy. The use of fuller’s earth in .processing animal and vegetable oils has never been a major one and has decreased to the point where it is included as a part of the miscellaneous uses in the US Bureau of Mines Minerals Yearbooks.

Palygorskite (attapulgitej fuller’s earth was first sold for drilling mud in 1941. The mar- ket for this use expanded slowly and has maintained a level of 7 to 10% of the total United States production during the last few years. Most of the fuller’s earth sold for drilling mud comes from the southern part of the Meigs-Attapulgus-Quincy district of Georgia and Florida. Palygorskite clays produced in this area are superior to most other fuller’s earth for muds used in drilling salt formations, but because of high water loss, they are inferior to bentonite where the rocks drilled contain no saltwater.

Fuller’s earth was used in significant quanti- ties as a carrier for insecticides and fungicides by 1950, and the market for this use has grown at a rather uniform rate since that year. In 1979, nearly 14% of the fuller’s earth produced was used for this purpose.

The use of fuller’s earth granules for absorb. -knt purposes began during the 1930s, but this

use did not expand significantly until the World War I1 period when fuller’s earth was used as an absorbent for greases, oil, water, chemi- cals, and other undesirable substances on the floors of factories, filling stations, canning plants, aircraft hangers, decks and engine rooms of ships, and other installations. The absorbent granules are porous and ordinarily weigh less than 30 Ib per cu ft. Because of their light weight, size, porosity, and absorbent properties, the granules are suitable for many uses, and since World War I1 many different markets for them have developed (Fig. 2 ) . Among other uses, they are now sold for litter and bedding for poultry, pets, and other animals, and as a soil conditioner in greenhouses and for golf courses. In 1982, 895,700 tons of fuller’s earth were sold for absorbent and filtering uses; this tonnage was nearly 53% of the total fuller’s earth produced in the United States that year.

The foregoing discussions apply only to those uses consuming sufficient quantities of fuller’s

~-

592

i

-. Industrial Minerals and Rocks

" 1966 1967 1969 1971 1973 1975 197'7 1979 1981

YEAR

FIG. 2-Fuller's earth sold or used by domestic producers for specified (Ampian. 1980, 1983).

. . i . .~ -:,.-;..>

earth to be classified separately by the US Bureau of Mines in the Minerals Yearbooks. In addition, smaller quantities of fuller's earth are or have been produced for many miscel- laneous uses. According to Oulton (1965), more than 90 different grades of fuller's earth are produced. Some of these grades are used for pharmaceuticals designed to absorb toxins, bacteria, and alkaloids; for treatment of dysen- tery: for purifying water and dry-cleaning Ru- ids, dry-cleaning powders and granules: for the manufacture of NCR (no carbon required) multiple-copy paper; for the manufacture of wallpaper: and as extenders or fillers for plastic, paint, and putty. Fuller's earth mined near Ellenton, FL, was used for making lightweight aggregate for the construction of concrete barges during World War 11 (Calver, 1957; Greaves-Walker, et al., 1951). Still other uses nf fuller's earth and its suitability for uses in new products are outlined by Haden and Schwint (1967), Haden (1972), and Haas (1970). One special use of fuller's earth is as a carrier of platinum catalysts that are made in

. . . ..?_.., . . .ii. r -

the United Kingdom from sepiolite clays minZd in Spain. Other uses of sepiolite fuller's earth (Chambers, 1959) are similar to those of the palygorskite (attapulgite) type mined in the

Some reports also note that fuller's earth is used in making cement. Probably the basis for these reports is the mining of the Twiggs Clay Member of the Barnwell Formation near Clinchfield, GA, and the use of the clay in making portland cement. It is used for this purpose mainly to obtain the desired chemical composition in the clinker from which the C* ment is made. The classification of this clay aS fuller's earth results from the fact that Twiggs Clay Member is mined for fulle1,S earth, and this unit is widely known in G e o r p as a source of fuller's earth,

Product Specifications

Product specifications have been tentativel? standardized for bentonite and (or) fullers earth sold for drilling mud, foundry-sand bond, absorbent granules, and oil bleaching and Will

United, States. .,.:

' .. .:, . . ..

, . I

1 '& . * . , E

be outlin the man) are prep. individua with eac

Drill in tions for gite) ful suspensic moisture

Suspen sion pro] suspensia 350 cc c aged mi point Cali 600 rpm according ments ou specificat Another the filtrat ume of w when test ing ro p troleum Accordin, mud qual ing at 60 pounds p, maximum mum. P; drilling- r specificati made wit1 per 100 requiremi P@ygorsk nies still I Yield is a leum lnst barrels of be made I quirement

Wet& (grit test) tonite or : coarser tl specified t in 350 c, agent. sti through 2. (API STI then driec original t fulfill the have no Palygorsk .

----.

's mined r's earth e of the

in the

earth is basis for ggs Clay Jn near

clay in for this

chemical 1 the ce- s clay as that the

fuller's Georgia

:ntativclS , fuller's nd bond. and will

.:.. >? '

Y: :

Clays 593

Moisrure-The maximum moisture content of bentonite when shipped from the plant where it is processed is 10% and that for palygorskite is 16%. Foundry Sand Bond Tentative specifications

for Western bentonite for bonding foundry sand are outlined in Steel Founders Society of America SFSA Designation l3T-65 issued in 1965. This specification requires the following characteristics and properties for Western bentonite, as tested by methods described in the specification: ( I ) water content shall not ex- ceed 12% or be less than 6%; (2) pH value shall be equal to or greater than 8.2, (3) cal- cium oxide content shall not exceed 0.70%, and (4 ) the liquid limit shall not be less than 600

he outlined briefly. Specifications for most of the many other products made from these clays are prepared to meet the requirements of the individual customer, and they commonly vary with each.

Drilling Muds: The most critical specifica- tions for bentonite and palygorskite (attapul- gite) fuller's earth for drilling muds are the suspension properties, wet-screen analysis, and moisture as shipped.

!. Suspension Properties-The test. for suspen- ' sion oroverties involves the oreoaration of a . . . . . suspension consisting of 22.5 g of bentonite in

350 cc of distilled water. The suspension is aged and the viscosity determined and yield ooint calculated from dial readines at 300 and

I

-, 600 rpm with a direct-indicating viscometer, ; according to procedure and equipment require- ~. ments outlined in American Petroleum Institute - specification API STD 13A, 5th edition, 1969. Z Another important suspension requirement is

the filtrate test, which is a measure of the vol- : ume of water lost from the prepared suspension 2. when tested in a vressurized filter Dress accord- 1 ..

: ing to procedurk outlined in American Pe- troleum Institute soecification API R P 13. According to these specifications, to he drilling- mud quality, a bentonite must have a dial read- ing at 600 rpm of 30 minimum, a yield point pounds per 100 sq ft of 3 times plastic viscosity maximum, and a filtrate volume of 13.5 maxi- mum. Palygorskite (attapulgite) prepared for drilling. mud must fulfill the same viscosity smcification as bentonite. but the susmnsion is

--.made ~. with water containing 40 g of sait (NaCI) per 100 cc of water. Yield point and filtrate requirements are not ordinarily specified for palygorskite-type drilling muds. Many compa-

.. nies still use a yield specification for bentonite. 1 Yield is a term used in earlier American Petro- .''' leum Institute specifications for the number of -. -. barrels of 15 centepoise viscosity mud that can 5. be made from a ton of bentonite. The yield re- .** - .. quirement is ordinarily 90 bbl per ton minimum. $. , Wer-Screen Analysis-Wet-screen analysis

(grit test) is a measure of the material in ben- e tonite or palygorskite (attapulgite) mud that is :..coarser than ZOO-mesh US Series sieve, The $specified test is made by mixing 10 g bentonite e in 350 cc water containing 0.2 g dispersing 5. ? agent, stirring, aging, stirring, and washing :- through a sieve with a specified spray system ?.(API STD 13A). The residue on the sieve is .I then dried, weighed, and the percentage of the . original bentonite is determined. Bentonite to '.?fulfil the specifications for drilling mud must

have no more than 2.5%' residue (grit) and .: palygorskite no more than 8% residue.

"Z

or greater ihan 850. Each foundry has its own green, dry, and hot-strength specifications for bentonite, which vary with the type of metal, size of castings, and foundry production proce- dures. Methods of testing strengths of henton- ite-bonded sands are outlined in detail in publications of the American Foundrymen's Society (Anon., 1962a, 1963). The tests re- quire the preparation of a specified mixture of bentonite, standard testing sand. and water: the

Ilt ..

to controlled procidures. Iron-Ore Pelletizing: Specifications for bento-

nite used for pelletizing taconite-type iron-ore have not been standardized, and several tests are used (Sastry and Fuerstenau, 1971; Wake- man, 1972). As green pellets must he capable ~ ' . 'of withstanding handling,'compaction, and dry- ing and the dry pellets must he even stronger, mixtures of bentonite, iron ore, and water are commonly tested for wet-drop strength, wet- compression strength, plastic deformation, and dry-compression strength.

Absorbent Granules: Most absorbent gran- ules marketed are prepared to fulfill the require- ments outlined in Federal Specification P-A- 1056A, Absorbent Material, Oil and Water (for floors and decks), outlined for purchases by the US General Services Administration. A simi- lar set of soecifications is outlined in the Ameri-

and absorbent characteristics required of gran- ules as outlined in the federal specification are listed in Table 2.

granules consist of a uniform mixture of min- erals of the silicate type. They also must be clean, uniform, and free of lumps or foreign

The specifications require that absorbent . -.

!

I l

i

I

i j

, . ,. .,

~- . 594 Industrial Minerals a n d Rocks

., .:, . TABLE 2-Characteristics of A h r b e n t Granules . .,,,-..I -

Characteristic Maximum .Minimum

Maner retained on a No. 6 US Standard Sieve Maner retained on a No. 30 US Standard sieve 99.0% . 52.0% .. Maner retained on a No. 40 US Standard Sieve . . 99.8% . . 73.0% Maner retained on a NO. 60 US Standard sieve 100.0% 90.0% Ability to absorb lubricating oil l ~ e r gram of sample) Ability to absorb distilled water (per gram o f sample) Solubility in distilled water 1.5% -

1 .O% 0.0%

- 0.8 ml "'0.9 rnl -

matter, and no more than 10% of them can pass through an 80-mesh sieve in the attrition resistance test. The attrition-resistance test is made by shaking with steel b d k on a screen, according to a specified procedure.

Fuller's Earfh for Bleaching Oils: Test meth- ods for evaluating bentonite and other types of fuller's earths for bleaching soybean and wtton- seed oils are outlined in the American Oil Chemists Society AOCS Official Method Cc 8b-52, revised April 1952, and AVCS Official, Method Cc Sa-52, corrected 1958. These speci- fications contain instructions on bench-type tests, including stirring time, heating rates and temperatures; approved equipment; quantities of raw oil and clay required; methods of color determinations; and so forth. They also require the comparison of the material tested with an official natural bleaching earth approved by the American Oil Chemists Society. The color de- termination of the bleached oils and their com- parisons with the oil bleached by the official earth in the same test are the basis for purchase specifications.

Geology

Mineralogy: The principal clay mineral in bentonite is smectite. according to the definition used in this chapter, and many fuller's earth deposits also consist chiefly of this mineral. The term smecrite is applied as a group name, and monrmorillonire is a mineral species name. This usage conforms to the growing acceptance of the term smectite and does away with the confusing use of montmorillonite as both mineral species and group names. Montmoril- lonite, including both sodium and calcium va- rieties. is the most common member of the smectite group occurring in bentonite. How- ever, saponite, a magnesian smectite, and hec- torite, a lithium-bearing magnesian variety, are the major minerals in some bentonites.

Smectite minerals occur in extremely small particles (Fig. 3 ) ; therefore, detailed informa- tion on them is difficult to obtain and is. in part.

:

based on theoretical considerations. A s the mineralogy of this group of clays is complex, the reader is referred to authoritative books and other references given in the introduction for detailed information on them, and only the following brief summary will be given here.

According to the most generally accepted structure, smectite consists of two silica tetra- hedral sheets with a central octahedral sheet. ' T'hc theoretical structural formula is (OH),&

..Al,Ol,,nH,O, and the theoretical ctpposition without interlayer material is SO,;. 66.7%; A1,0,, 28.3%; and H,O, 5 % . However, smec- tite always differs from the foregoing theoretical . . formula and composition (Table 3) because of substitutions of various ions for silicon in the tetrahedral coordination and for aluminum in the octahedral sheet. Furthermore. the substi- tuted ions are thought to be commonly of dif- ferent valence than the theoretical ion replaced. which results. in an unbalancing of the charge in a unit of smectite. This charge deficiency is balanced by exchangeable ions. which vary con- siderably and result in further differences in the compositions of smectite. Cations which are exchangeable in bentonite include sodium, cab cium, potassium, magnesium, lithium. and hy- drogen. The exchange capacity of most benton- ite is within the range of 60 to 150 milli-

Unit layers of smectite are thought' to be stacked with the oxygen layer of one silica tetrahedral sheet adjacent to the similar layer In the neighboring unit. Only a very weak bond exists between neighboring units. and water 01 other polar molecules can enter between ilnlt layers causing the lattice to expand in the! dl- rection. This expansion by polar molecules and the collapse of expanded units with heat, which can be recognized by X-ray diffraction methods. is applied in studying smectite and distinguish- ing members of this group from other clay minerals.

The ion-exchange characteristics have.an im- portant role in controlling or influencing the physical properties of bentonite and the bento- nitic fuller's earths. In general, those bentonite'

' ~

: .

equivalents per 100 g. . .

FIG. 3--. bentonite (API sum, E.I. D w (

that hav ion have loidal pr dominan other CI propertif valuable ing thixc ties usua out bene other ch, not ordii The type role in c As point lonites h Propertie moderatf strength) hand, hi

- Minimum

O:O% 52.0% 73.0% 90.0%

- 0.8 mi 0.9 rnl - -

IS. AS the

: books and Is complex.

duction for d only the given here. ly accepied Silic:. trtra. edral sheet. is iOH),Si, composition 0,: -66.1%; vever, smcc- g theoretical ) because of ilicon in the iluminum in :. the substi- cionly of dii- ion replaced. I f the charge deficiency i* ich vary con- :rences in the is which arc sodium, cal-

ium. and hy- most benton- o 150 milli-

,ought to bc of one silica imilar layer in 'y weak bond and water or between uni t

id in the c di- molecules and th heat. which :tion methods. Id distineiiish. ,m other cla!

cs have.an in>- nfluencillg tht and the bento'-

bentonite'

- .._ . ... . ~. . . . . . . . . . . - .. . . . . .

Clays

-

595

...

1

FIG. 3-Ekcfron micrograph of bentonire from Clop Spur, W Y (API snmple 2 6 ) . Micrograph by E.I. Dwornik, LIS Geological .~ Survey.

that have Na' as the dominant exchangeable ion have very high swelling capacities and col- loidal properties, and those in which Ca** is the dominant ion tend to swell, little more than other clays. Because of their high colloidal properties, high-swelling sodium bentonites are valuable as drilling muds and other uses requir- ing thixotropic suspensions. The calcium varie- ties usually have little value for such uses with- out beneficiation by the addition of soda ash or other chemicals, and even when so treated, are not ordinarily as efficient as the sodium types. The type of exchangeable ion also has a major role in controlling the bonding characteristics. As pointed out by Grim (1962),,sodium ben-

itonites have very strong foundry sand bonding . properties after drying (dry strength), but only

moderate strengths when moist or wet (green strength). Calcium bentonites. on the other

, ,.

nd, have high green strengths and low to

moderate dry strengths. However, part of these differences in bond strengths may be due to particle size or other characteristics, and there IS some evidence that the dry strength of some calcium bentonites can be increased by length- ening the mulling (mixing) time in the prepara- tion of foundry sand.

All bentonites contain mineral impurities, which vary considerably in type and quantity present. A few are contaminated with minor quantities of clay minerals other than smectite, such as kaolinite and illite. The common non- clay minerals in bentonite include those listed in the older definition by Ross and Shannon (1926). and minor quantities of most of the accessory minerals in volcanic rock also may be present. Selenite is abundant in many de- posits, and some beds contain carbonate veins and concretions. Zeolite minerals and opal, cristobalite, or other forms of poorly ordered

596 - ~.

Industrial Minerals and Rocks

TABLE 3-Chemical Analvsm of Clays

1 2 3 4 5 - 6 7 8 9 -10

SiO, 54.34 54.62 50.20 49.72 49.91 53.95 53.96 43.98 45.20 '46.77 19.92 20.08 16.19 16.39 17.20 0.14 8.56 38.46 37.02 37.79 1.11 2.36 4.13 3.10 2.17 0.03 3.10 - 0.27 0.45 A 4 0 ,

Fe,O, FeO 2.17 1.03 - 1.00 0.26 - 0.19 0.03 0.06 0.11 TiO, 0.11 0.11 0.20 0.58 0.24 Tr 0.24 0.01 1.26 0.02 CaO 0.33 0.40 2.18 4.19 2.31 0.16 2.01 0.32 0.52 0.13

2.21 2.15 4.12 2.56 3.45 25.89 10.07 Tr 0.47 0.24 2.65 2.26 0.17 0.66 0.14 3.04 0.03 0.14 0.36 0.05 0.45 0.35 0.16 1.55 0.28 0.23 0.39 0.48 0.49 .1.49 0.01 0.01 0.18 0.16 -

11.73 11.78 15.58 12.21 15.77 9.29 9.79 2.58 1.55 '0.61 4.50 4.58 7.57 5.71 7.70 5.61 . 11.51 14.59 13.27 12.18 . . - - - 1.71 - - .

MgO Na,O K,O MnO SO, H,O- H,O+ co 1

p,o,

~ Tr. - - - 0.01 0.04 - - - - -. - - - - - - - . - -

- - ~- 0.06 - - - - - ' " 0.10

. ~. , ., :- *,

- . 0.03 - - - - - - - - - 0.24

. -- - . . _ I * < , - - - . - - 0.73 -

- 0.03 - - - Tr

- - - - - - - - - - - .

S Ba0 Z"0 C LiO, F

- - - - '. _' - -

- . - - - - - - - 1.22 - - - - - - ---- -

99.71 99.89 100.50 100.21 99.47 99.56 99.85 100.59 100.47 -100.21 - Total Less 0 for S . .. - 0.37 ._ - ...',.

99~84

1. Bentonite. bluegray, clay spur bed, Belle Fourche, SO (Foster, 1953) 2. Same as 1 but Oxidized to olive green IFOSter. 19531. 3. Bentonite. Polkville, MS (Ross and Hendricks. 19341. 4. Fuller's earth. Combe Hay, Somerset. United Kingdom (Kerr et SI.. 1950) 5. Bentonite. Chambers. AZ [Chetol (Kerr et el.. 19501. 6. Hectorite, Hector. CA (Kerr et SI.. 1950). 7. Palygorskite lattapulgitel. Anapuigus. GA (Ken et ai.. 1950). 8. Halloysite, Eureka, Utah (Ken et .I., 1950). 9. Kaolinite. Macon, GA (Ken et el.. 1950).

10. Kaolinite. St. A~stel I , United Kingdom (Ken et .I.. 19501.

silica are present in some bentonite deposits in western United States and at several other places in the world. Some deposits are con- taminated with incompletely altered parts of the rock from which they formed. The vitric latitic tuff remaining in the bentonite at Cheto, AZ (Sloane and Guilbert, 1967), is an example of this type of material.

The principal fuller's earth deposits other than the bentonite type consist of palygorskite (attapulgite) and sepiolite. According to Brad- ley (1940), palygorskite has an ideal formula of (OH,),(OH),Mg,Si,0,;4H,O, but substi- tution of AI3* for either Mg*+ or Si'+ takes place. It consists of two silica chains linked in amphi- bolelike structures and has both monoclinic and orthorhombic symmetry (Christ et al.. 1969).

,Sepiolite, (Si,?) (Mg,,)0,,(OH),(OHz);6H,0, is thought to have three pyroxene-type chains (Grim, 1968), and, therefore, the unit cell is somewhat larger than for palygorskite. Both palygorskite and sepiolite typically occur in fibrous and elongate lathlike particles. Sepiolite

- is also the mineral forming meerschaum (See - "Meerschaum). :

Other nonbentonite fuller's earths include an uncommon type of rock called opal claystone (Heron, et al., 1965). This rock is more than three-fourths opal or another form of poOdY ordered silica, and the remainder is moot- morillonite and other mineral impurities. ]* was mined in South Carolina in the early Pan of this century and used for bleaching oil, and it is the raw material to be mined near Rimml. SC, to supply a fuller's earth plant Under construction in 1972. Nonbentonite clays [ha' have been used as fuller's earths. in the.Pvt include the Anna kaolin in Illinois, halloysite In Utah (Schroter and Campbell, 1940), and glacial clays in Massachusetts. In additio0,t" these nonbentonite clays, there are extenSIVe deposits of fuller's earth consisting of vev impure montmorillonite that are not ordinardY thought of as being bentonite. .Two such de. posits are the Porters Creek Clay (Paleocene) in the Mississippi Embayment region and the

.. .

Twiggs CIS tion (Eocei

Occurrei Jurassic ai States and deposits m, younger. 1

high-swelli: duced has age, and n has come f Shale. Th, mainly in and Mioce bentonite c type, in th tiary age. California, upper Tert be Late Mi known Ch is in the B and deposi also in PI] Meadows I

by Denny ~

age, and if are among

Most be bodies alii zone. Son miles, and ticular one diameter. to more t t posits ord contact wit one with c hydrotherfi shaped an, directions.

Most be low-swellir soaplike te face tend when the become lii posits undt bluish gra: the surfac. Typical o have a poi alternate s. Outcrops I

a cracked semble all

Most b,

F 9 10 -

15.20 46.77 37.02 37.19

0.06 0.1 1 1.26 0.02 0.52 0.13 0.47 0.24 0.36 0.05 0.49 1.49

0.27 0.45

T I - - -

1.55 0.61 13.27 - 12.18 - -

Eerschaum (see

inhs include an opal claystonc

:k is more than form of poorly inder is mont-

impurities. I! n the early pan :aching oil, and ed near Rimini. th plant under :onite clays thnl ths in the P S I ois, halloysite in

In addition to e are extensive lsisting of veF .e.not ordinarily

Two -such d e lay (Paleocene) region and the

:II, 1940), and

.. . .. . . ~. .

Clays

Twiggs Clay Member of the Barnwell Forma- tion (Eocene) in Georgia.

Occurrence: Though bentonite deposits of Jurassic age are extensive in western United States and elsewhere in the world, virtually all deposits mined to date are of Cretaceous age or younger. All hut a very minor tonnage of the high-swelling Wyoming-type bentonite pro- duced has been mined from beds of Cretaceous age, and more than three-fourths of the total has come from a single formation-the Mowry Shale. The Southern or calcium bentonite is

. . mainly in formations of Cretaceous, Eocene, -~ and Miocene age. .The abundant miscellaneous

bentonite deposits, other than the high-swelling type, in the western states are mainly of Ter- tiary age. Deposits scattered through Nevada,

1 California, Oregon, and Idaho are mainly in . upper Tertiary rocks, and many are thought to i be Late Miocene or Pliocene in age. The widely : known Cheto bentonite near Chambers, AZ, .:- is in the Bidahochi Formation of Pliocene age, :~ and deposits mined in western Oklahoma are '; also in Pliocene rocks. Deposits in the Ash

Meadows district, NV, occur in rocks mapped :. by Denny and Drewes (1965) as Pleistocene in

age, and if this age assignment is correct, they are among the youngest bentonites in the world.

Most bentonite occurs in beds or lenticular bodies aligned along a definite stratigraphic zone. Some beds extend for more than 200

. miles, and other deposits, particularly the len- ticular ones, are only a few hundred yards in

- diameter. Deposits mined range from about 1 to.more than 30 ft in thickness. Bedded de- posits ordinarily have a characteristic sharp

-. contact with underlying rocks and a gradational . one with overlying strata. Deposits formed by

hydrothermal processes tend to be irregularly - shaped and to grade into the host rock in all

directions. ,& c-- Most bentonite, including both the high and ?- 7- low-swelling types, has a characteristic waxy or .: soaplike texture. Pans of deposits near the sur-

face tend to be light-yellowish green or gray .. when the natural moisture is present and to -become lighter in color when they dry. De- . posits under Considerable overburden tend to be

., bluish gray. The change to lighter shades near z. the surface is related to the oxidation of iron. Z Typical outcrops of high-swelling bentonite ?= - have a popcornlike or frothy texture caused by galternate swelling and drying of the bentonite. &Outcrops of low-swelling types commonly have s a cracked appearance thought by some to re-

Most bentonite in North America and else-

I .

-

_- ,:.

semble alligator hide.

where occurs in sedimentary rocks and was formed in place from volcanic ash or tuff. Some deposits have been formed by hydrothermal al- teration of volcanic or other igneous rock. and other deposits of nearly pure smectite may be accumulations that were transported and de- posited in marine or alkaline lake water with only minor postdepositional alteration.

The extensive palygorskite (attapulgite) full- er's earth deposits in the southern part of the Meigs-Attapolgus-Quincy district, Georgia and Florida (Fig. 4), occur as tabular lenses and discontinuous beds in the Hawthorn Formation of Miocene age. This clay is green and bluish gray, and most of i f has a waxy or soaplike texture.

In addition to the deposits in the United States, palygorskite fuller's earth is also mined. in the following regions: (1 ) Pout district near Mbour, Senegal (Wirth, 1968); (2) Ukrainian district, USSR (Ovcharenko et al., 1967); and (3) Mudh district, India (Siddiqui, 1968). The Senegal deposits are in marine beds of Early Eocene age. The Ukrainian palygorskite is in- terbedded with bentonite. Deposits in India occur between fossiliferous limestones and ap- parently are marine in origin.

Insofar as the authors are aware, the only sepiolite fuller's earth mined at the time this report was written is in the Vallecas and an- other district in Spain (Anon., 1972b). How- ever, economic sepiolite deposits have been dis- covered recently in the Ash Meadows district, Nevada (private communication). The Spanish deposits occur in an evaporite sequence .of Ter- tiary age.. The Nevada deposits are closely as- sociated with calcium, sodium, and magnesium bentonites of Pleistocene age.

Origin: The evidence for most bedded bento- nite having formed from volcanic materials transported considerable distances in the atmo- sphere was presen!ed by several geologists early in the century, including Hewett (1917), Wherry (19171, and recently by Slaughter and Earley (1965). This conclusion is based pri- marily on the purity of smectite, on the fact that the nonclay minerals in bentonite are angular and of the type occurring in volcanic rock, rather than mixtures of rounded grains charac- teristic of detrital sediments, and on the pres- ence of relict shard textures in many bentonites (Ross and Shannon, 1926). Ample evidence supports the conclusion that the parent ash of most bentonite was deposited under marine conditions, but a few deposits apparently ac- cumulated in alkaline lakes (Papke, 1969). As would be expected, different bentonites have

formed from volcanic rock of somewhat dif- ferent types, and the most common parent ma- terials range from andesite to rhyolite in com- position. Opinions differ concerning the process and time of alteration of the ash. Several au- thors have noted that change in ash would have begun with its contact with water, hut when the alteration was completed is questionable. Papke (1969) believes that one type of bentonite de- posit formed in alkaline lakes soon after deposi- tion and another type formed more slowly as the result of alteration by ground water. Altera- tion by ground water requires burial by younger rocks and probably regional uplift and a con- siderable interval of geologic time. In the au- thors' opinion, changes have taken place in bentonite deposits throughout virtually their en. tire geologic history. Some deposits may have been altered extensively before burial beneath younger rocks. However, the prominent cherty zone below several beds points to the downward transport of silica by ground water from alter- ing deposits; this must have taken place after burial.

Bentonite formed by hydrothermal activity

j i

, .. !

! i

,. ~

occurs in Nevada (Papke, 1969). California (Kelley, 1966), Spain (Anon., 1972b), a d elsewhere. Deposits of this type commonly are associated with other minerals known to have formed by hydrothermal processes. They also tend to occur in irregularly shaped bodies ra- ther than in beds, and they ordinarily grade into the host rock through partially altered zones. The distribution and shape of bentonite formed hydrothermally are commonly controlled by fault zones, joints, and other geologic features

Alteration of volcanic ash or tuff in restricted alkaline lakes heated by hot-spring activity is also thought to have formed bentonite .(Arne? et ai., 1958). The hectorite deposits in Cab fornia probably formed this way, and this clay passed through an intermediate stage in which most of the.ash was altered to zeolite. A mag nesium bentonite called amargosite formerly mined near Shoshone, CA, also formed by the alteration of vitric volcanic material.by hot springs (Sbeppard and Gude, 1968).

Though the authors have doubts about the theory. some bentonite deposits are thought 10

providing access for heated water, . .

have smect tion o

rocks, ties, i plied (Sidd bayev

posits Rober from mass. nonigt

AS they h er's ea tite an p a h a in Ge< ably f g have t miner: eviden been F these

water This t! forma:

Distrit

BENTC calciiii sissipp

YTeagi -posits and 1, differe and 11 these 1 sippi, I

The mainl) region rangin cene , et ai., mitten LA (C mined which The V' Forma tonite

by w

(Papk

palygo

. .

Nor

.

F.

California >72b), and nmonly are wn to have

They also I bodies ra- y grade into ered zones. uite formed ntrolled by gic features

in restricted activity is

nite (Arne!. sits in Call- ;nd this clay ge in which ite. A mag- te formerl! formed by

terial ‘by hot 8 ) . ts about the e thought to

have been deposited mainly in the form of smectite minerals. According to this explana- tion of origin, smectite minerals, having formed by weathering of volcanic or other igneous rocks, were transported, separated from impuri- ties, and deposited. This theory has been ap- plied to explain the origin of deposits in India (Siddique and Bahl, 1965), the USSR (Tazbi- bayeva and Galiyev, 19721, and Nevada (Papke, 1969). Bentonitic fuller’s earth de- posits in the United Kingdom were thought by Robertson (1961) to have been transported from smectite-rich soils on the European land- mass. Such soil woutd have formed mainly on nonigneous rocks.

As most fuller’s earth deposits are bentonites, they have the same origins; however, some full- er’s earths consist of minerals other than smec- tite and may he of quite different origin. The palygorskite (attapulgite) fuller’s earth deposits in Georgia and Florida are one type that prob- ably formed in a different way. These deposits have been investigated by several geologists and mineralogists, and no one has found convincing evidence of any volcanic materials having ever been present. The first author has investigated these deposits in detail and believes that the palygorskite in them formed in place from sea- water evaporating in a . tidal-flat environment. This theory is essentially the same as the “neo- formation” idea of Millot (1964). ’

Clays , . 599

’ Distribution of Deposits ’ North America: United States-SOUTHERN

BENTONITE AND FULLER’S EARTH-Southern or, calcium bentonite is now mined in Texas, Mis- sissippi, Alabama, Oklahoma, and Louisiana (Teague, 1972). Undeveloped bentonite de- posits occur in South Carolina (Robinson, Buie, and Johnson, 1961). At present, at least 17 different hentonite.mining operations are active, and 1 I plants are processing bentonite, One of these plants is in Alabama, four are in Missis- sippi, one is in Louisiana, and five are in Texas. ; -The bentonite deposits in Texas (Fig. 4 ) are I mainly in an extensive belt in the Coastal Plain ’~ region. Valuable deposits. occur in formations

ranging in age from Late Cretaceous to Mio- f cene (Hagner, 1939; Maxwell, 1962; Fisher Set al.. 1965). The bentonite is mined inter- !. mittently near Mineral Springs, Lincoln Parish, -LA (Gann, 1971) Deposits also were formerly : mined in the Vernon Parish (Welch, 1942), I which is in the west-central part of Louisiana.

The Vernon Parish deposits are in the Fleming Formation (Miocene) which also contains ben- tonite in Texas. Most of the bentonite pro-

-.

i

s,.

duced in Mississippi is mined near Aberdeen, Monroe County, where the American Colloid and International Minerals & Chemical Corps. operate plants. Bentonite is also mined inter- mittently in Smith County, and clay that is pre- sumably bentonite is produced in Pearl River County. The deposits mined in Monroe County are in the Eutaw Formation of Late Cretaceous age. Deposits mined in Smith County are in Oligocene rocks, and the deposits in Pearl River County are of Miocene age (Bicker, 1970). The bentonite processed near Sandy Ridge, AL, oc- curs in the Ripley Formation [Upper Creta- ceous] (Monroe, 1941).

Fuller’s earth is produced mainly in the southern states; and the Meigs-Attapulgus- Quincy district, Georgia and Florida (Fig. 4), is the leading fuller’s earth-producing district in the United States. The deposits mined in this district occur in the Hawthorn Formation of Miocene age. Those in the northern part of the district consist chiefly of diatomaceous mont- morillonite containing minor quantities of other clay minerals and clastic nonclay mineral im- purities. Some of the deposits in the southern part of the district are the purest palygorskite (attapulgite) mined in the world. The fuller’s earth mined in central Peninsular Florida also occurs in the Hawthorn Formation, and this clay consists chiefly of montmorillonite.

Large deposits of fuller’s earth occur in the Twiggs Clay member of the Barnwell Forma- tion of Eocene age. These deposits crop out in a belt extending across central Georgia seaward from the fall line. The Twiggs Clay member is now mined and process<d by the Georgia Ten- nessee Minine Co. at Wrens. GA (Patterson.

,. , .

..

- 1972), and it was formerly mined at several other places in this state. The Twiggs Clay member consists mainly of montmorillonite and cristobalite (Brindley, 1957) or opal (Carver, 1972).

In 1973, five plants were actively producing fuller’s earth from the Porters Creek Clay of Paleocene age. This formation extends from west-central Alabama across the northeastern part of Mississippi, the western parts of Ten- nessee and Kentucky, southernmost Illinois, and into southeastern Missouri. Most of the Porters Creek Clay consists of a mixture of montmorillonite and other clay minerals, and much of it contains appreciable quantities of cristobalite and nonclay mineral impurities (Sims, 1972).

Fuller‘s earth used mainly in bleaching ani- mal and vegetable oils is now produced in Texas, and historically this state has ranked

600 industrial Minerals and Rocks

with the leading producers. The fuller's earth produced in Texas is mined from bentonite beds.

WYOMING OR HIGH-SWELLING BENTONITE DEPOSITS-The Northern Rocky Mountains- High Plains region has led the world in the production of Wyoming or high-swelling ben- tonite since the first mining of this clay. In 1973, 16 plants were processing bentonite in this re- gion. The major producing districts (Fig. 4) are as follows: ( I ) the northern and western Black Hills districts, Wyoming, Montana, and South Dakota; (2) Kaycee-Midwest, Wyoming; (3) Greybull-Lovell, Wyoming and Montana; (4) Vananda, Montana; and ( 5 ) Chinook- Malta-Glasgow, Montana.

Virtually all the bentonite produced in the Northern Rocky-High Plains region' occurs in sedimentary formations of Cretaceous age. Most of the bentonite produced in the Black Hills district has been mined from the Clay Spur Bentonite Bed, which is in the uppermost part of the Mowry Shale (Davis, 1965; Knech. tel and Patterson, 1962). High-swelling ben- tonite deposits in the Newcastle Sandstone have also been mined, and a small tonnage has been produced from beds in the Belle Fourche Shale. A bentonite in the upper part of the Pierre Shale was mined on the southern flank of the Black Hills before and during World War I1 and processed for use as water softener. A very low swelling bentonite having.the properties of the southern-type bentonite is now mined on a small scale from a bed in the Pierre Shale in the northern Black Hills.

Most of the bentonite mined in the Kaycee- Midwest and Greybull-Love11 districts occurs in the Mowry Shale, but some beds in younger formations are also mined in these districts (Anon., 1969h). The bentonite produced mainly for taconite-bonding purposes in the Vananda and Chinook-Malta-Glasgow districts, Montana, occurs as extensive beds in the Bearpaw Shale (Berg, 1969, 1970), which is considerably younger than the Mowry Shale.

HEcToR1TE-virtually all the hectorite mined to date has been near Hector, CA, the type locality. The hectorite occurs as a waxy soft nodular layer ranging from 6 to 8 ft in thick- ness. It is associated with sandstone and clay beds of Tertiary age that accumulated in an alkaline lake environment. The beds below the hectorite contain travertine formed as the re- sult of hot-spring activity (Ames, et al., 1958). The valuable hectorite deposits are overlain by Quaternary basalt.

A large deposit of hectorite has been discov-

ered recently in the Amargosa Valley, &. : fornia (private communication). Plans for min- $ ing and processing this clay were in an ad. vanced stage of preparation when this repon .; was written.

In addition to the Hector and the Amargosa - districts, hectorite also occurs 16 miles north of Amboy, CA, and in Yavapai County, AZ . (Norton, 1965). Deposits not known to the ' , authors probably occur at other localities, and there are many areas where the' geologic con. ditions are favorable for more discoveries.

tonite (other than the Wyoming type and hec- torite) and fuller's earth deposits are scattered throughout the western states (Fig. 4) . In gen- eral, bentonite production from these deposits has been small, as compared with that from the Wyoming and Southern types, because many of these clays are of lower quality and all of them

'.are more distant from the major consumers. One district in which bentonite has been mined continuously for a long time is in the vicinity of Chambers [Chetol, A 2 (Kiersch and Keller. 1955). This bentonite is a low-swelling clay used as bleaching earth and 'in making desic- cants. Bentonite used for preparing livestock feed is mined in southwestern Idaho, southern California. and probably elsewhere. Deposits in central Oregon are used in the preparation of retardants used in fighting forest fires. Some of the white bentonite mined in Nevada is used in pharmaceuticals and beauty aids. A bento- nite io the Ash Meadows district composed Of saponite (Papke, 1969) was mined extensively several decades ago, and other deposits in the state have been mined for use in water imped- ance and for other purposes. Low-swelling 01 calcium-type bentonite also occurs and is duced in the region containing the Wyoming 01 high-swelling bentonite, Low-swelling bento- nites are mined from deposits in the northern Black Hills and the flanks of the Big HOT Mountains. This bentonite is marketed manly for foundry-sand bonding, --

The most active fuller's earth-producing dis- tricts in the western states are in Kern CoUntYv CA; plants operated by Excel Minerals are at McKittrick and Taft, and thz Panamint Mar- keting plant is at Maricopa. These plants Pro' cess a clay mined from the Monterey Shale of Miocene age. Some beds in the Monterey Shale consist chiefly of diatoms and montmorillonite. and probably the raw material mined is of th's composition. Absorbent granules, insecticide carriers, and other fuller's earth products are prepared for market. In addition to the de-

. . I .. :**. 1

OTHER DEPOSITS IN WESTERN STATES--Ben-

-

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posit and I forni decol

er's f The I tons, tonitt use c reserx very for b classe sever; high and a earth tons. here, est gr past \.

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and Con.

-Ben. hec.

tered gen.

losits n the G-uf ihem nen. lined :y Of d e r .

lesic- jtocl (hein ?osiis ation jome used ento- :d of ,ively i the iped- 1g or pro-

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Clays ~. i ' 601

posits in Kern County, bentonite near Olancha and probably deposits at other localities in Cali- fornia have been processed for filtering and

RESouncEs-Resources of bentonite and full. er's earth in the United States are very large. The reserves of bentonite are at least one billion tons, and the total resources, including all ben- tonite that will be eventually suitable for one use or another, are considerably larger. This reserve estimate of one billion tons includes very large deposits that have a quality buitable for binding iron-ore pellets but that would be

1 classed as submarginal for 'drilling .mud and several speciality uses. The reserves of very

. high quality drilling-mud bentonite are limited ". and are much in demand. Resources of fuller's ; earth are tentatively estimated at two billion ., tans. However, almost any figure could be used - here, if all the clays equal in quality to the low- : est grade material used as bleaching clay in the

past were included. A large part of the fuller's

. decolorizing agents in recent years,

~-

earth resources is in the extensive Porters Creek Clay and the Twiggs Clay Member of the Barn- well Formation. These deposits are suitable for use in absorbent granules and certain other fuller's earth products, but they are not used in drilling mud and several of the speciality products.

Canada-Bentonite occurs in beds of Cre- taceous and Tertiary ages at many places in western Canada (Ross, 1964; Spence, 1924). The major producing districts (Fig. 5 ) are Onoway (Baroid Canada, Lid.) and Rosalind (Dresser Industries, Inc.) in Alberta and in the Pembina district (Pembina Mountain Clays, Lid.) in Manitoba. Bentonite has also been mined near Princeton, B.C., and deposits near Avonlea, Sask. (Anon., 1971), and along the Mackenzie River in the vicinity of Inuvik. N.W.T., have been investigated by industry.

The deposits mined in Alberta are in the Edmonton formation, the uppermost Creta- ceous unit in this region. Those mined at Rosa-

FIG. 5-Map showing bentonite districts in Canada.

602 Industrial Minerals and Rocks

lind are nearly flat lying and are 8 to 10 f t thick. The deposits mined at Onoway are 2 to 2Y2 f t thick, and the overburden removed from them has an average thickness of about 7 ft. Benton- ite deposits mined in the Pemhina district are in the Vermillion River formation (Upper Cre- taceous), which consists mainly of black shale. The bentonite near Princeton. B.C., is of Ter- tiary age, and it is interbedded with lignite (Spence, 1924).

Several grades of bentonite are produced in Canada. The swelling bentonite mined in Al- berta is sold for use in drilling mud, foundry. sand bond, fire retardant, and stock-feed pel- letizing (Ross, 1964). The bentonite produced in the Pembina Valley is a low or nonswelling variety. It is processed in a plant at Morden, Man., and some is activated with sulfuric acid in a plant at Winnipeg. This bentonite is used for foundry-sand bond, insecticide carriers, and pelletizing animal feed. The activated bentonite is used for bleaching mineral lubricating oils and waxes, re-refining used lubricating oils, gnd decolorizing animal and vegetable oils.

According to Ross (1964), only a very few million tons of bentonite reserves have been proved in Canada. However, the potential re- sources of bentonite in the country must be very large, considering the large areas now known to contain Fcattered deposits and the general similarities of strata to Cretaceous and Tertiary rocks in the United States known to contain bentonite.

Mexico-The German firm Siid-Chemie AG with its Mexican affiliate Tonsil Mexicana SA has operated a bentonite plant in Puebla since 1967 (Anon., 1969k), and another plant is ac- tive intermittently at Monterrey. Bentonite and fuller's earth also occur in QuerCtaro, Michoa- c h . and Guanajuato, and a few of these de- posits have been mined on a small scale (Es- quivel and Zamora, 1958). Apparently, most Mexican bentonite deposits occur in sedimen- tary rocks, and some of these are of the non- marine type.

South America: Argenrino-Bentonite de- posits are scattered throughout several prov- inces in Argentina (Bordas, 1947). The princi- pal deposits mined and the 1969 production (Anon., 1971b) are as follows:

Tons Principal Deposits Province Produced

Rio Chico Chubut 5.286 El Alamo y Las Hegueras Mendoza 19.799 El Catalin Neuquen 4,622 Del Lag0 Camino y Rob Rio Negro 14,427 La Emilia y Cristina S a n Juan 18,005

Total 62.139

A few thousand tons of fuller's earth are also produced each year. The fuller's earth deposits mined are in La Rioja and Rio Negro provinces.

Brazil-A plant processing montmorillonite : clays for use as foundry-sand bond was-built ; a t Sacramento, Minas Gerais, in 1962 (Anon,, 7 1962). Bentonite has also been found at sev. . era1 other localities in the country.

Peru-Bentonite and fuller's earth occur io f the provinces of Pisco, Canete, Paita, and Con- ' tralmirante Villar, and elsewhere (Caherra, 1963). Bentonite has been mined and usetin iron-ore pelletizing- in Peru for several years (Anon., 1967a), and present production is cs- timated to be 20,000 tpy (Anon., 1973a).

Europe: Cyprus-A low-swelling calcium bentonite is mined in the Troulli district near Kambia (Anon., 19691). A few thousand tons are produced annually. Part is processed in a small plant at Vassiliko, and part is shipped to Israel for heneficiation and use in several prod- ucts (Anon., 1970e).

Czechoslovakia-Bentonite. occurs i n ~ the northwestern, central, and eastern parts of :

Czechoslovakia (Gregor, 1967). The bentonite is chiefly of the calcium and magnesium types, and it formed from rhyolite tuffs. It is as much as 70% montmorillonite; the nonclay minerals present include cristobalite. Bentonite reserves in Czechoslovakia were estimated to be I O mil- lion tons.

Apparently, the most productive bentonite district is in the northwestern part of the coun- try, inasmuch as a bentonite processing plant having a yearly capacity of 100,000 .tons was built at Zelenice (Anon., 19691). One-third-of the bentonite produced in this plant is reported to be available for export.

France-The company SociCtC Fransabe des Bentonites et Dkrives SarL. markets several grades of bentonite. mined principally in cen- tral France (Anon., 39691). The deposits mined are presumably those in the Department of Vienne and the Limousin region that have been worked for many years (DCribCre and Esme. 1943). Other bentonite and fuller's earth de- posits are in Vaucluse (Mormoiron, Sainte- Radegonde. and Apt) and PyrCnCes. Most bentonite and fuller's earth-deposits in France are chiefly smectite, hut those at Mormoiron are mixtures of smectite and palygorskite-(Mil- lot, 1964).

Greece-Rather extensive deposits of benton- ite occur in the eastern part of the island Of Milos (Anon.. 19691). The deposits are as much as 100 f t thick. Apparently they formed by the alteration of ash or tuffs of Pliocene age in a marine environment (Wetzenstein, 1972). One plant near deep water operated by the

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I bond was built in 1962 (Anon.,

:en found at sev. .intry. .'s earth occur in :, Paita, and Con. .where (Caberra, lined and used in for several years production is es. on., 1973a). swelling calcium oulli district near ew thousand tons' is processed in a part is shipped to e in several prod-

occurs in the eastern parts of 1 ) . The bentonite magnesium types, lffs. It is as much nonclay minerals jentonite reserves Ited to be 10 mil-

iuctive bentonite part of the coun- processing plant

100,000 tons was 21). One-third of plant is reported

iet6 Franqaise des markets several

rincipally in cen- he deposits mined : Department of 3n that have been -ibire and Esme. fuller's earth de- ,rmoiron, Sainte- Pyrenies. Most eposits in France ,e at Mormoiron lalygorskite (Mil-

:posits of benton- of the island of deposits are as

,ntly they formed 'S of Pliocene age ,tzenstein, 1972). operated by the

, . : . . . ._ ,, . .

Cla)

Greek company, Silver and Barytes Ores Min- ing Co., has a yearly capacity of 200,000 tons. Three other companies are also mining benton- ite on this island (Wayland, 1971). .The ben- tonite producers on Milos have been particu- larly successful in selling bentonite for iron-ore pelletizing, mainly because of the nearness of deposits to deep-water shipping. Bentonite pro- duced on this island is also sold for drilling mud and foundry-sand bond, and for other purposes.

. In addition to the deposits on Milos, benton- , ite also occurs on Mikonos where three com-

panies have been active in recent years. With production on both islands, Greece ranks

.. among the leading producers of bentonite. = Hungary-Bentonite occurs at scattered lo- - calities in Hungary. Recently, bentonite-

processing facilities were concentrated at Mod, under the supervision of personnel of the Na-

' tional Ore and Mineral Mining Enterprise (Sondermayer, 1967). The new plant is re- ported to have a capacity for processing 100,- 000 tpy of raw bentonite. Both natural calcium and sodium-exchanged bentonites are produced for several different uses (Anon., 1970d).

Italy-Italy is one of the leading European bentonite producers. The deposits. mined are on the island of Ponza, off the western coast, and on Sardinia. The Ponza deposits are near Cala dell Acqua. They are in volcanic rock and

.. were formed by hydrothermal alteration of rhyolite tuffs (Lupino, 1954). The average thickness of these deposits is about 10 m, and 2.9 million tons is estimated to be present

. '(Anon., 1969i). Several grades of beqtoqite are produced on Ponza, and one of them is a colloidal white bentonite that brings a high price for speciality uses. This white bentonite is one of the few bentonites imported hy the United States.

The deposits on Sardinia are mined by In- dustria Chimca Laviosa SPA, an Italian com- pany (Anon.. 1970b), and NL Industries, Inc. (Wayland, 1971). The Italian company is min- ing the Pedra de Fogu deposits near Alghero. . and grades suitable for drilling mud, iron-ore

i pelletizing. civil engineering applications, water : treatment, and wine purification are produced. 5 .. The deposits mined occur in altered rocks

(Pietracaprina and Novelli, 1972). The benton- L. ite mined is the swelling type. It is approxi- k mately 70% montmorillonite. and the impuri-

.ties are chiefly free silica, illite, and calcite. The deposits mined by NL Industries are near - Nurallao (Anon., 1969g). These deposits are in Miocene marine sediments. and they are

i underlain by Jurassic limestone and trachyte 3, flows. This bentonite is sold primarily for drill-

. '

s I

-

t

..._ . - . . .

IS 603

ing muds in countries bordering the Mediter- ranean Sea and in the Near East.

Poland-Bentonite deposits of Eocene and Miocene age occur in southern Poland: these are processed for use as bleaching clay (No- wacki and Ciechomska, 1964) and probably for other uses.

Romania-Romania has been one of the ma- jor East European bentonite-producing coun- tries for several years. The bentonite is mined underground in the Alba-lulia-Ocana Mures district (Neacyu, 1969), and apparently it is produced elsewhere. The yearly production of bentonite in Romania is estimated to be more than 100,000 tons (Huvos and Sondermayer, 1968).

Spain-Bentonite and fuller's earth occur at several places in Spain. The most productive bentonite deposits are in the Cab0 de Gata re- gion in Almeria. These deposits have formed by the hydrothermal alteration of rhyolite and andesite igneous rocks (Anon., 1972b; Martin Vivaldi and Linares, 1968, 1969). The more intensely altered parts of deposits contain kaolinite, alunite, and jarosite. Other parts contain minor amounts of palygorskite and sepiolite, which presumably indicates an excess of magnesium at the time of alteration. Fuller's earth deposits consisting mainly of sepiolite occur at Vallecas and elsewhere in the Tagus basin (Anon., 1972b; Huertas, et al., 1971). The deposits are i n an evaporite sequence of Tertiary age. The annual output of fuller's earth in the Vallecas district is approximately 14 kt. Absorbent granules, insecticide car- riers, and material5 for other uses are produced.

Switzerland-Bentonite is mined in Switzer- land and used in bonding foundry sands (Grim, 1962).

Unired Kingdom-Calcium montmorillonite clays occur at many places in the United King. dom, and fuller's earth has been mined since the Roman period nearly 2000 years ago (Anon., 1969f). Fuller's earth districts now active are at Redhill in Surrey, Combe Hay south of Bath in Somerset, and Woburn in Bedfordshire. In addition to these districts, large deposits of cal- cium montmorillonite have been discovered in the Swindon-Abington district in Berkshire by the Institute of Geological Sciences (Poole and Kelk, 1971; Poole et al., 1971), and other de- posits occur near Clophill in Bedfordshire, and Maidstone in Kent.

The deposits in Surrey and Bedfordshire are in the Lower Greensand, which is the upper formation of the Lower Cretaceous Series (Holmes, 1950). These deposits consist of hard bluish-gray clay having a soapy feel. They are in beds of-imegular thicknesses, and at

I

'I .. .: . , . .. ,. . ;.-.:_ . . .

Industrial Miner ~- . 604

places as many as eight beds of clay are present in the Lower Greensand.. Thicknesses of clay mined range from 5 to 8 f t . Most mining is by stripping methods, but deposits in the Combe Hay district are mined underground.

The fuller's earth at Combe Hay district oc- curs in the Great Oolite series of Middle Juras- sic age. These fuller's earth deposits are com- monly 6 to 7 f t thick. As in several bentonite deposits in the United States, the fresh clay in the Combe Hay district is bluish green, and the weathered parts of the deposits are yellowish. ' Fuller's earth production in the United King- dom has quadrupled since 1945, and 176,000 tons was produced in 1970 (Anon., 1 9 7 2 ~ ) . Probably the biggest market is for foundry-sand bond, and some of the clay is treated with soda ash for this use. Sodium-exchanged fuller's earth is also used in pelletizing animal feeds, treating domestic water supplies, and for sev- eral uses requiring swelling or thixotropic prop- erties, including civil engineering uses, drilling mud, and for water-impeding purposes. Ap- proximately a fifth of the fuller's earth pro- duced is acid activated; this clay is sold mainly for alkylation catalysts.

USSR-The principal bentonite deposits in the USSR are in the Volga Region, western and central parts of the Ukraine, Transcaucasia Re- gion, Kazakhstan, and Central Asia (Lebedin- skii and Kirichenko, 1972; Anon., 1970a). Smaller bentonite resources also occur in east- ern and western Siberia, Crimea, and 'in the northern Caucasus.

Several large bentonite deposits of Lower Miocene age occur in the Cherkassy district (Ovcharenko et al., 1967), which is located along the border between the Cherkassy and Kiev regions in the Ukraine. The deposits consist of five layers having maximum thick- nesses ranging from 1.5 to 8 m. Though most of this bentonite consists chiefly of montmorillo- nite containing minor quantities of detrital min- eral impurities, one layer as much as 2 m thick is mainly palygorskite (attapulgite). This paly- gorskite was discovered during geological stud- ies in 1954, and it is the first fuller's earth de- posit of this composition found in sufficient quantities for mining in Russia.

Most bentonite produced in Azerbaijan in the Transcaucasia Region is mined from beds of Cretaceous age (Seidov and Alizade, 1966), but younger deposits are also present in this region. The bentonite in Azerbaijan is interbedded with tuff and calcareous sedimentary rocks and is thought to have formed mainly by the decom- position and alteration of volcanic ash in a ma-

,ais and Rocks .. 3

:

.: rine environment. However, some deposits m y have been altered from other rocks by hydro- thermal solutions. . .~

The scattered bentonite deposits in Kazakh- stan occur mainly in Lower Tertiary rocks (Akhmed, 1963; Tazhibayeva and Galiyev. 1972). They are thought to have altered from - hydromica and related minerals in an alkaline and deoxydizing environment in inland seas in regions of arid climate. The mica minerals a p parently were transported from weathered rocks in land areas. . . ,

! .. The principal uses of bentonite in USSR are in the manufacture of heavy clay products, .: drilling mud, and iron-ore pelletizing, and mi- nor quantities are used in purifying oils, water, "

and wine. In 1967 about 1.5 million tons was produced (Lebedinskii and Kirichenko, 1972). and the total consumption was about 3.4 million' tons. Imports to fulfill requirements came from --; Italy, Czechoslovakia, and Hungary. ._ -W.esf Germany-Lower Bavaria has bgen a major. producer of smectitic fuller's earth"and bentonite for many years. The two major pro- ducers are Siid Cbemie AG, which has a plmt at Mooseberg (Anon., 1969k), and Erbsloh and Co., which operates a plant at Landshut (Anon., 1969e). The deposits are mined mainly by open-pit methods, but some underground min- ing is still done. Both companies produce sodium-exchanged bentonite for use in foundry- sand bonding and for use in several products requiring colloidal properties. Smectite clays are also acid activated and exported to several countries for processing oils and waxes.

in many places in Yugoslavia, and the total resources in the country are very large (Anon.. 1969111). The bentonite is processed, including some sodium exchanging, at several places. The three largest producers have a total annual plant capacity of 100,000 tons, of which 30,000 can be acid-activated. Yugoslavia exports bentonite mainly to East European countries, but minor tonnages are also shipped to West European markets. The quantity exported in 1968 Was 23,745 tons.

the Ginovci deposits, 81 km northeast of Skople (Konta, et al., 1971). These deposits are m lacustrine beds of late Pliocene age, and they formed by alteration of dacite tuffs. The hen- tonite is reported to be more than 85% smec- tite and contains 1.2% quartz and 0.5% Cns- tobalite. Reserves of the three best grades of bentonite in these deposits are estimated to p" 1.4 million tons. The Ginovci bentonite 1s

. -. ..

.

Yugoslavia-CaIcium-type bentonite ,occurs '

The best quality bentonite in Yugoslavia is in .

converted intc Bentomak pla

Africa: AI{ mined in the I of Algeria (AI production in 25,000 to 38 processed in ~

shipped across at Oudja.

The bentoni in both altere< sedimentary r( dran, et al., I ! essentially pur the deposits all traces of kaolii deposits are I (

Kenya-Ber has been mil foundry-sand I

Malagasy-! scale in this co reported to ha\ t ryin 1969 (AI

Morocco- F occur in the C localities near This bentonite mation of the It occurs in b lagoonal or lac Production in . 20,000 to 30,O

Another ty1 magnesium m (rhassoul in FI in the Tamdafc valley (Jeanne! sold for severa Ghassoul is a t lonite containi: in five separate IS to 80 cm.

Mozambiqu< near Impampv 26 tpd began p bentonite also Marques in IC marketed in Et

Senegnl-La ing principally CUI in the Pout ~

(Wirth, 1968) cene sediment; cording to the in Senegal are

-

Clays 605 deposits may

i in Kazakh. :rtiary rocks .nd Galiyev, altered from .I an alkaline dand seas in minerals ap.

Athered rocks

in USSR are aY Products. :in& and mi. g oils, water, jion tons was enko, 1972). u t 3 4 million t s came from Y. a has been a 1's earth and '0 major pro. h has a plant I Erbslah and lshut (Anon., d mainly by rground min- nies produce ;e in foundry- era1 products mectite clays :ed to several 'axes. tonite occurs ind the total large (Anon.. ;ed, including 11 places. The ~ annual plant h 30,000 can xis bentonite :s, but minor :st European in 1968 was

lgoslavia is in :ast of Skopje posits are in Ige, and they Ts. The ben-

85% smec- d 0.5% CnS- est grades of iimated to be bentonite is

by hydro. converted into a'sodium type in the modern Bentomak plant near Kriva Palanka.

Africa: Algeria-Calcium-type bentonite is mined in the Marnia and Mostaganem districts of Algeria (Anon., 19691). Algerian bentonite production in recent years has ranged from 25,000 to 38,000 tpy. Part of this clay is processed in a plant at Marnia, and part is shipped across the Moroccan border to a plant at Oudja.

The bentonite in the Marnia district occurs in both altered rhyolite masses and as beds in sedimentary rock of Lower Miocene age (Sa- dran, et al., 1955). Much of this bentonite is essentially pure montmorillonite, but some of the deposits altered from volcanic rock contain traces of kaolinite and some of the transported deposits are 10 to 20% kaolinite.

Kenya-Bentonite in the Athi River valley has been mined intermittently for use as foundry-sand bonding (Thompson, 1952).

Malagasy-Bentonite is produced on a small scale in this country, inasmuch as 99 tons were reported to have been exported from that coun- try in 1969 (Anon., 1 9 6 9 ~ ) .

Morocco-Extensive deposits of bentonite occur in the Camp Berteaux district and other localities near Taourirt in eastern Morocco. This bentonite is the product of the transfor- mation of the glassy materials in volcanic ash. It occurs in beds interstratified with Miocene lagoonal or lacustrine deposits (Millot. 1964). Production in recent years has ranged from . 20,000 to 30,000 tpy (Anon., 19691).

i Another type of clay consisting main lysf .. magnesium montmorillonite called ghnrsoul

(rhassoul in French) is produced from deposits : in the Tamdafelt district in the middle Moulaya

valley (Jeannette, 1952; Eyssautier, 1952) and sold for several uses requiring absorbent clay. Ghassoul is a brown to black waxy montmoril- lonite containing 26 to 28% MgO. It occurs

. . in five separate beds ranging in thickness from I I5 to 80 cm.

Mozambique-A bentonite processing plant near lmpamputo having a capacity of 24 to

: 26 tpd began production in 1963. High-quality ' bentonite also has been produced at LnurenGo ' Marques in recent years, and some of it, is

marketed in Europe (Anon., 1973a). Senegal-Large fuller's earth deposits consist-

ing principally of palygonkite (attapulgite) oc- cur in the Pout region and elsewhere in Senegal (Wirth, 1968). The deposits are in lower Eo- :. ~cene sedimentary beds of marine origin. Ac- r. cording to the published test data, the deposits ' in Senegal.are not as high grade as some of the i

'

i

best fuller's earth mined in the United States, but they are used for several of the same prod- ucts. Most of the fuller's earth produced in the Pout region is shipped to European markets.

South Africa-Bentonite is mined in Trans- vaal and Orange Free State, and i t is reported to have been discovered near Plettenberg Bay, Cape Province (Anon., 1972j; Woodmansee and Murchison, 1969). Production has in- creased in recent years and now virtually all of South Africa's bentonite requirements are ful- filled by the domestic output. Apparently, the deposits mined consist chiefly of smectite min- erals. The authors are unaware of any develop- ment of the palygorskite (attapulgite) deposits at Springbok Flats that are widely referred to in the geologic literature.

Tanganyika-The production of a few tons of bentonite in Tanganyika in 1958 was re- ported by Ross ( I 964).

TanzaniaSlat ick (1969) noted the produc- tion of 203 tons of bentonite in Tanzania and small quantities mined in other years.

Asia: India-Major fuller's earth deposits occur in at least five states in India, and benton- ite occurs at several localities. Probably the best known deposits are in the Barmer district, Rajasthan (Siddique and Bahl, 1965). They are believed to be transported clays deposited in a marine embayment during late Tertiary time, and the clay minerals formed by the weathering of igneous rock. Other deposits occur in Tertiary beds in Gujarat and in Mio- cene rocks in Jammu and Kashmir; those in Madras and Bihar are of Jurassic age. Fuller's earth mined in the Mudh district is of Eocene age, and it is chiefly palygorskite (Siddiqui, 1968). Indian bentonite is used for drilling mud, foundry-sand bonding, water sealant, and other uses. The deposits in Gujarat are near the coast,'and some of this bentonite is sold in Europe and elsewhere. Apparently most of the fuller's earth produced is used domestically for purifying oils and processing fibers.

Japan-Two rather distinct types of smectite mineral deposits occur in Japan (Takeshi and Kato, 1969); one is called bentonite and the other, acid clay. The bentonite is composed chiefly of sodium montmorillonite, and the acid clay is montmorillonite in which H- has substi- tuted for exchangeable M p and Ca++. Deposits of both types occur at several places in Japan. Bentonite altered from bedded rocks called Green Tuff of Miocene age occur in Hok- kaido and several places in Honshu (Takeshi and Kato, 1969; Urasima, Syoya, and Suzaki, 1966). Large deposits formed by hydrothermal

-

~- .~

... . - , Industrial Minerals and Rocks

alteration of rhyolite and rhyolitic tuffs occur in Higashikambara-gun district, Niigata Prefecture (Takeshi, 1963). The Teikoku deposit, one of several in this district, is principally sodium montmorillonite. Bentonite formed by diagenic alteration of tuff beds occurs at Usui-gun, Gunma Prefecture, and several places in Yama-

i gata Prefecture (Takeshi and Kato, 1969: Omori, et al., 1961). Several of these deposits

- contain appreciable quantities of zeolite, cris- tobalite, and detrital minerals, which contami- nate the montmorillonite.

Large deposits of acid clay formed by dia- genic processes occnr at Tsuruoka-shi district, Yamagata Prefecture, at Kitakanbara-gun, Nii- gata Prefecture, and elsewhere. Acid clay formed hydrothermally also occurs at several places in Niigata.

The yearly bentonite production in Japan is estimated to be approximately 300,000 tons, and demands are increasing (Takeshi and Kato, 1969). Several companies are now active and are processing bentonite in different ways for domestic markets and export. Japanese henton- ite is used for foundry-sand bond. drilling mud, several pelletizing and briquetting bond uses, agricultural engineering, soil-improving agent, additives for ceramic raw materials, car- riers for agricultural chemicals, paper making, .filler for water-based paint, clarifying and coag- ulation liquids, making organic-clad bentonite, and for other uses. Acid clay is used mainly to produce activated clay by a sulfuric acid-treat- ment process. Aluminum sulfate and synthetic gypsum, made with the addition of calcium, are recovered as byproducts of this process. The activated clay is used in decolorizing lubricating oils and other oils and fats, for hygroscopic and absorptive applications, and as petroleum cata- lyst. Acid clay is also used i n the manufacture of globular alumina gel, silica gel, fine powdery silica, filler for noncarbon duplicating paper, and for other uses. The exported Japanese bentonite and acid clay are shipped primarily to countries in southeastern Asia, and petroleum catalysts are apparently the principal products shioned. . . ~ ~

Pakistan-Bentonite occurs at several places in Pakistan. Deposits in the Bhimber district of Azad Kashmir of probable middle Pliocene age have been mined since 1958 (Ali and Shahn. 1962). The bentonite is used for several pur- poses, including the preparation of surgical dressings. A plant for processing activated bentonite at the rate of 20 tpd was under con- struction at Gujrat in 1962 (Nawaz, 1962).

South Korea-The Dong Bo Clay Industrial

Co. operates a bentonite plant in Seoul (Anon., 1973a). The mines are located in North Kyongsang Province.

Turkey-Bentonite and fuller’s earth occu.r-at several places in Turkey. Bentonite has been produced on a small scale for domestic use as foundry-sand bond, wine purification, insecti- cide carriers, and other uses for several years. In 1973, plans were underway for expansion of mining and processing of sodium bentonite (Anon., 1973). Fuller’s earth presumably has been used locally for centuries.

The older productive deposits apparently are at Killik, Eskisehir Province, and Kursunlu and K W k , Cankiri Province (Anon., 196.5). The sodium bentonite is near Resadiye, Tokat (Anon., 1973).

Oceania: Ausfralia-A few hundred tons of bentonite have been produced in Australia in recent years (Kalix, 1971), and there has been intermittent mining of fuller’s earth for a long r i a . The bentonite produced in 1970, ihe last year for which figures are available, was 136 tons from Nanango Mineral Field and 100 tons from Ipswich in Queensland, and 116 tons from lake deposits at Marahagee and Woodanilling in the southwestern part of Western Australia. In that year, 58,244 tons of bentonite was im- ported from the United States, and the average f.0.b. value was $23.08 per ton. Considerable interest in bentonite in Australia has developed because of its possible use in pelletizing iron ore and other uses, and it seems likely that valuable deposits will be found. Fuller’s earth was mined on a small scale in the Dubbo dis- trict, New South Wales, as recently as 1969. New Zealand-Bentonite mining began in

New Zealand at Porangahau, Hawke’s Bay, In 1940, and in recent years it has also been pro- duced in the Harper Hills region of Canterbury. The Harper Hills deposits mined are in lower Eocene beds, and apparently they formed by the alteration of volcanic materials deposited in a marine environment (Ritchie, et al., 1969). Bentonite also occurs in beds of Miocene and probable Late Cretaceous ages in this region. The bentonite mined in the Harper Hills regton is a tow-swelling iron-rich variety, Eontainlng as much as 10% kaolinitic clay. New Zealand bentonite is used mainly for foundry-sand bond and as an additive to ceramic material, but I t may be suitable for other uses, including Pel- letizing taconite iron ore.

Evaluation of Deposits

Exploration: The exploration for bentonite and fuller’s earth deposits, as for virtually all

.. ‘ j minerals, re .- - geologic occ ‘j testing, and

standing of tial in the I

reviewing al on deposits rocks in the field investig but reconna for many d beds are ger cause of the to develop a by shrinkagc swelling ben posits are no bentonite, ai required.

Once loca ing or drilli widely used overlying rc equipment a torily, partic the top of augers are a ploration, bt to be unsatii skite (attapu are common1 and a fishtai sandy overb with water.

.i ting head is approached, equipment. found to be plete recover also used in hard rock in

Testing: T earth is han6 universally a tioos. As a their valuabl: different way the widely Y. the many d. purchasers f< single grade Slurry of dit procedures, and even m, limits. Clear procedures i: the part of ti

Jul (Anon., in North

.nh occur a t :e has been iestic use as ion, insecti. :vera1 years. :xpansion of n bentonite jumably has

'parenth are . - .ursunlu and 1965). The

dred tons O( AOsrralia in ere has beer, h for a long 970, the last de, was 136 and 100 tons 16 tons from iodanilling i n iustralia. In lite was im- 1 the averagc Considerablc as developed lletizing iron s likely that 'uller's earth 5 Dubbo dir- i as 1969. ng began in vke's Bay, in Is0 been pro- : Canterbury. are in lower ormed by the :posited in a

al., 1969). Miocene and , this region. r Hills region y, containing New Zealand ry-sand bond iterial, but i t ncluding pel-

_- for bentonite . virtually 811

C

minerals, requires first an understanding of the geologic occurrence of deposits, then sampling, testing, and appraising of results. An under- standing of the geology of the deposits is essen- tial in the early stages and is gained by first reviewing all published and other information on deposits under consideration or on similar rocks in the region. The second step is geologic field investigations, which may require mapping,

-but reconnaissance studies have been adequate for many deposits. The Wyoming bentonite beds are generally easy to find. in the field, be- cause of their tendency to swell when wet and

: to develop a "popco'rn" or frothy texture caused by shrinkage when drying. The calcium or low- swelling bentonite and some fuller's earth de- posits are not as easy to find as the swelling-type . bentonite, and extensive drilling is commonly required. i . Once located, deposits are explored by auger- ing or drilling. The auger method has been widely used for bentonite, mainly because the

: overlying rocks can be penetrated by such ,' equipment and the bentonite sampled satisfac- '

torily, particularly if the hole is cleaned when . the top of the bentonite is reached. Power

augers are also used in some fuller's earth ex- ploration, but they have generally been found to be unsatisfactory in searching for palygor- skite (attapulgite) type deposits. These deposits are commonly explored with drilling equipment, and a fishtail bit is'used to penetrate the soft sandy overburden, the cuttings being flushed with water. A core barrel with a toothed cut- ting.head is used when the top of the clay is approkhed, and the clay is sampled with suth

-equipment. A double-tubed barrel has bet2 found to be effective in obtaining more com- plete recovery in some deposits. Core drilling is

~. also used in exploring for hectorite, because 06 hard rock in the overburden.

j. Testing: The testing of bentonite and fuller's earth is handicapped by the general absence of

' universally accepted procedures and specifica- tions. As a result, these clays are tested and their valuable properties are expressed in many different ways. Some of the reasons for this are

, the widely varying properties of the clays and the many different specifications outlined by

i purchasers for many uses. The purchaser of a 1 single grade of bentonite may require tests of a i slurry of different concentrations, preparation

procedures, aging, temperature specifications, i. and even measurements of liquid and plastic ' limits. Clearly, the absence of standardized test ! procedures indicates the need for an effort on :. the part of the American Society for Testing &

-

. .

:lays 607 Materials or another organization, with the cooperation of industry, to establish useful pro- cedures having wide application, Rather than go into details on the many empirical and tentative test procedures that are now in use in evaluat- ing bentonite and fuller's earth and that are likely to be superseded by more scientific and technically accurate methods, only a few gen- eralized comments on tests will be made in the following paragraphs.

Bentonite and fuller's earth are tested for use in drilling mud by adding water and mixing slurries of specific concentrations and measur- ing viscosity, yield, yield point, and filtrate (a measure of wall-building properties), and mak- ing a wet-screen analysis, according to standard procedures recommended by the American Pe- troleum Institute (Anon., 1969, 1969a). The Oil Companies Materials Association (Anon., 1969b) in the United Kingdom also has specifi- cations for testing drilling muds. Tests for foundry sand-bonding properties require prepa- ration of standard mixtures of bentonite and sand and measurements of compression strengths of carefully prepared test pieces in a 'manner similar to the methods outlined by Fisk (19461, the American Foundrymen's So- ciety (Anon., 1962a; 1963), and the Steel Founder's Society of America (Anon., 1965a). Tests for taconite pelletizing bonds vary con- siderably (Davison, 1969), but some require certain strengths in pellets measured by- the number of times they can be dropped in speci- fied intervals onto a hard surface without break- ing (Stone, et al., 1971; Sastry and Fuerstenau,

. 1971; Wakeman, 1972). Oil-bleaching tests of fuller's earth and bentonite are commonly made according to procedures described by the American Oil Chemists' Society (Anon., 1958). Ross (1964) and Nutting (1943) also have given procedures for evaluating fuller's earth for use in bleaching oils. Tests for a variety of different insecticide, dust diluents, and carrier uses have been described by Weidhaas and Brann (1955). Most tests for absorbent gran- ules are made according to procedures in Fed- eral Specifications P-A-l056A, Absorbent Ma- terial, Oil and Water (for floors and decks), available from the US General Services Ad- ministration. No standard procedures have been developed for testing bentonite for use in water impedance, but rather detailed procedures for testing bcntonites for canal and pond sealants have been described by the Colorado State ... University Experiment Station (Dirmeyer and

As swelling bentonites are generally more Skinner, 1968). . .

608

-

Industrial Minerals and Rocks

deposits is as much as I M ) f t (Teague, 1912). and beds of the same thickness have been stripped from low-swelling bentonite in one dis. trict in Arizona. The overburden stripped from fuller's earth deposits ranges from a few feet to

The rocks overlying most bentonite and full- er's earth deposits are soft and can be.loaded di. rectly by self-propelled or pushed scrapers, but in places they must be loosened by bulldozers and rippers before loading. Some of the over. burden above fuller's earth near Attapulgus, GA, and Quincy, FL, contains limestone and cemented sandstone that must be blasted. Vol- canic rocks above hectorite deposits in Cali- fornia also must be blasted where stripping is done. Bentonite is mined underground by the square-set method in the New Discovery mine near Beatty, NV (Papke, 19691, and insofar as the authors are aware, this is the only benton- ite now mined underground in North America.

-.Heolorite in California and bentonite the Ash Meadows district, Nevada (Papke, 1969), and the Chambers [Cheto], Arizona, district, were formerly mined underground. Early in this century, overburden was stripped from full- er's earth near Quincy, FL by hydraulic meth- ods, and the clay was transported by trams.

Most bentonite and fuller's earth produced in other countries are also strip mined, but under- ground methods are used in a few places. in- cluding the Combe Hay district in the United Kingdom (Anon., 1969f). Deposits in this dis- trict are selectively mined by hand, using com- pressed air picks. The clay is extracted in lumps 3 to 18 inches across, and it is hauled to under- ground storage facilities in mine cars drawn by electric locomotives. It is loaded as needed from the storage dumps onto.tNcks and hauled to the plant.

Because of variable physical properties, most bentonite and some fuller's earth deposits are selectively mined. Bentonite from a single pit or bed may be separated into as many as thrqe stockpiles at the plant, each with different physt- cal properties. Various grades of bentonite suit- able 'for different uses are then prepared from the separate piles and by blending cray from. more than one pile. Blending bentonite as it is dumped on stockpiles, using earth-moving Or cultivating equipment to obtain a uniform clay. is also common practice. The properties of fuller's earth, and particularly the palygorskite (attapulgite) type, vary considerably, but de- posits tend to be more uniform than bentonite. Commonly, an entire deposit will be suitable for one product, and another deposit in the Same

.:

. -,

.

more than 75 ft. . ' i

i

suitable for uses requiring colloidal properties and low-swelling ones are used in other ways, a preliminary indication of the potential value of bentonite can be determined by a swelling test. Perhaps the most common test is the sim- ple procedure of adding 2 g of dried and ground bentonite to a 100-ml graduate filled with dis- tilled water and determining the volume of the settled bentonite in milliliters (Ross, 1964).

Mineralogical Investigations: In addition to the testing of the type outlined in the foregoina . . paragraphs. information on the mineralogical and chemical composition of hentonote and full. er'r earth is also required. Mineralogical com- position. includlng the purity and undesirable contaminant,. is determined In some company laboratories. Other companies ohtain informa- tion of this type from consultants w h o are ex- perienced in the use of X-ray, electron micro- scope, differential thermal analysis. petrographic microscope, and other methods of investigating clays.

Appraisal of Field and 1,aboralory Results: The final step in the evaluation of bentonite and fuller's earth deposits involves the synthesis of data collected during the held investigations. sampling and testing, and other laboratory pro- g r a m Maps are prepared locating drill huleg and showing the thicknerse5 and qualtty of clay and thicknes,es of overhurden. Reserves of various grades of clay are calculated. and the mining cost is determined from such maps and from geologic and engineering notes taken dur- ing the fieldwork.

Preparation for Markets

Mining Methods: In the United StateS, vir- tually all bentonite and fuller's earth are mined by stripping methods. Bulldozers and scrapers or pans are most commonly used in removing overburden, but one company stripping near Attapulgus, GA, operates a large walking drag- line powered by electricity for stripping. In the typical pit, the overburden is removed in panels, the clay mined by loading trucks with dragline or endloaders, and the overburden from an ad- jacent panel shifted to the mined-out area. One company hauling on privately owned roads op- erates trucks having 100-ton capacity, but most hauling requires use of public highways and lighter trucks. Thicknesses of overburden re- moved vary considerably. Most Wyoming-type bentonite mined is under less than 30 f t of over- burden, but in a few places overburden is as much as 40 ft thick. The thickness of over- burden removed from some southern bentonite

district may different use

Beneficial Both bentor by simple I moval of w volatile mat The Wyomi delivered to 30% moisti or calcium-t fuller's eartt matter and processed bt or 8% wate may contaii Moisture cc fuller's eartl those of bei however, hat ture require1 minerals pre ules when co

In most pl some sort of chunks befor er's earth USI ing to impr products. Ir fed into a p the clay is th 'A in. in dia by gas or oil. in diam and operation in v, and a I fuller's earth dryers varies The desirabli colloidal gra greatly if .th temperature likely to be loo" to 200" in the main < kept at temp 1964). Tern? earth range Part of the : and the high

The dried ways. In son much of the product is gl or other pulv ite and mu, ground to a!

. . - . . . .~ ..._ ... .~ . . .- " . I . . , ... .~

igue, 1972). have been

re,in one diS. trlPPed from a few feet to

lite and full. be loaded di. scrapers, but ’Y bulldozen of the over. Attapulgus.

mestone and :llasted. Val. isits in Cali. 2 stripping is iound by the Fcovery mine SXinsofar

only benton- (rth America. :onite in the apke, 1969). ona, district. Id. Early in red from full. iraulic mcth- by trams. 1 produced in d, but under- w places, in. n the United its in this dis- 3, using com- cted in lumps iled to under: ars drawn by ‘d as needed (s and hauled

,perties, most deposits arc

1 a single pit nany as three ifferent physi- ,entonite suit- repared from ig clay from .tonite as it is th-moving or uniform clay. properties of : palygorskitc ably, but de- ,an bentonite. ,e suitable for

in the same

CI - district may have the properties required for a different use.

. BeneBciation and Processing Techniques: Both bentonite and fuller’s earth are processed by simple milling techniques that involve re-

. moval of water and, in some instances, other volatile matter, and grinding to suitable sizes. The Wyoming or high-swelling bentonite, when

. delivered to the plant, contains approximately 30% moisture; the free water in the southern or calcium-type bentonite is about 25%. Some

.’ fuller’s earth contains as much as 50% volatile

. matter and 10% .undesirable impurities. The processed bentonite ordinarily contains only 7 or 8% water, but because it is hygroscopic, it

’’ may contain considerably more when used. Moisture contents of most freshly processed fuller’s earth are approximately the same as

’- those of bentonite. Most absorbent granules, however, have been heated beyond the tempera- ture required to drive off hydroxyl water in the-

. minerals present, and any moisture in the gran- -- ules when consumed has been absorbed. ;: In most plants, the raw clay is passed through ~’ some sort of a clay “slicer” to break up the large

chunks before drying. One plant processing full. er’s earth uses an extruding process .before dry- ing to improve. properties desired in certain products. In this process the crushed clay is fed into a pugmill, where water is added, and the clay is then extruded as rods approximately ‘/i in. in diam. Drying in most plants is done by gas or oil-fired rotary dryers as large as I O f t indiam and 65 f l long. A fluid-bed dryer is in operation in one bentonite plant at Col~ny,

- WY, and a similar dryer is used in processing fuller’s earth at Meigs, GA. The temperature in dryers varies with the intended use of the clay. The desirable properties of both bentonite and colloidal grades of fuller’s earth are reduced greatly if the clay is heated too much. The temperature in dryers processing bentonite is likely lo he approximately 800°C at the inlet, 100” to 200°C at the outlet, and 400” to 500°C in the main drying zone. The bentonite itself is kept at temperatures of less than 150°C (Ross, 1964). Temperatures used in processing fuller’s earth range from 150” to 650°C. The lower part of the range is used for colloidal grades and the higher part for absorbent granules.

The dried clay is ground and sized in several ways. In some plants, rods in rotary dryers do much of the grinding, but most of the powdered product is ground with roll and hammer mills or other pulverizers, and screened. Most benton- ite and much of the fuller’s earth used is ground to approximately 90% finer than 200

;

609

mesh (US Standard sieve size). Some fuller’s earth for special markets is reported to be 95% finer than IO-micrometer particle size. Granu- lar grades of bentonite are also sold, and the wide use of absorbent granule-type fuller’s earth requires the preparation of a coarse product. The preparation of coarse absorbent granules is, in effect, a .beneficialion process, because much of the fine and medium-grained sand impurities in the fuller’s earth are in the size fraction discarded.

Hectorite and some southern bentonite, in addition to being processed like other bentonite, are beneficiated by a hydroclassification process. In this process, the clay is dispersed in water and pumped into a multistage concentrating cir- cuit where nonclay and other undesirable ma- terials are separated and removed. The slurry is then passed through drum or spray-type dry- ers, and the concentrate is ground. A high- value material is prepared in one plant by cen- trifuging a dilute slurry.

Transportation: Several types of packaging are used for both bentonite and fuller’s earth. For other than bulk shipments, multiwalled paper bags, some of which have plastic liners, are most common. Fiber drums are used for specialty products sold in rather small quanti- ties. Metal drums of 100-lb capacity are re- quired for some uses, particularly absorbent granules used aboard ships and where lengthy periods of storage or repeated handling are necessary. One French company uses the mod- ern containerized method for export shipments (Anon., 1969j). MQSI of the granules sold for animal litter are packaged in 10 to 30-lb paper bags, and packaging is a major item in the cost of the product.

The method of transporting bentonite and fuller’s earth depends on use and location of markets. Most of the processed bentonite is shipped by rail in bulk hopper cars, but boxcars and bulk trucks are also used. Bagged benton- ite is commonly palletized for shipment by either rail o r truck. Trains carrying only ben- tonite are used for large shipments to distant points and for overseas consignments. Ore carrier-type ships having bentonite as the only cargo are commonly used for Great Lakes and overseas shipments. The bentonite transported this way is only partly dried at the point of origin and is shipped semicrude. This method makes it possible to load and unload it by bulk- handling equipment, avoiding the costs of bag- ging, but it requires further drying and grinding at or near the place used. Much of the benton- ite used in pelletizing taconite ore, as well as

- -.

- _. - _

610 Industrial Minerals and Rocks

most of that sold in the European markets, is handled in this way.

Fuller’s earth is transported in a similar man- ner, except that orders are not sufficiently large to permit trainload or some of the other bulk. handling methods. Though some fuller’s earth is transported unbagged in special cars, most is bagged for rail transportation. Trucking is also used more extensively in the transponing of fuller’s earth than for bentonite, because orders tend to be smaller and are delivered directly to the warehouses of distributors. Granules for this use are commonly delivered by truck to warehouses of the distributing chain store.

Synthetic and Organic-clad “Bentonite“

A plant (Fig. 6) operated by Barold Div., N L Industries, Inc., at Houston, Texas, making synthetic mica-montmorillonite began produc- tion in 1970. An early announcement of this plant indicated that one of the products was hectorite (Anon., 1970). Published mineralogi-

cal reports related to the research on the de. velopment of this synthetic material refer to a randomly interstratified alumina montmorillo- noid (Granquist and Pallack, 1967; Granquist, et al., 1972) and SMM, which stands for sya- thetic mica-montmorillonite (Wright, et d., 1972). The principal product made in 1972 was advertised in a company pamphlet as BARASYM SMM. It consists of small stacks of thin, parallel, irregular platelets, having an equivalent diameter on the order of IOOOA and a thickness of about 1OA. This material is recommended for use in catalytic cracking, hydrogenation/dehydrogenation, double-bond isomerization, and disproportionation, and it may be a base for reforming catalysts and a component in hydrotreating catalysts. As a petroleum-cracking catalyst, BARASYM SMM is reported to be intermediate in activity be- tween silica-alumina and zeolitic catalysts. to ‘hai.e.a high selectivity for gasoline, and pccdnct distribution similar to silica-alumina catalysts.

FIG. &Synthetic “benronire” planr, Housron, Iexos (courresy Boroid Div., NL Industries Inc. ) .

-.i

3 _ ? ... 8 -. .-

$

.- 1 .The compar

it has typica

Apparent: True:

Typical analy (as received

Trace analysi

Surface area: on calcinatioi Saturation vo

N, sorption Hg porosir (excludine

Cation exchir Accessible * per 8

* To pyridii

Synthetic t Kingdom by under the br et al., 1970) urally occun fluoride. It p the same us developed fol

For severa ite has been c trade name product is pi original inorg tonite is repi cation. This clay because drated are re clay-mineral sorbing water

- Organic-clad paint; to gel < having super metal, ability high tempera:

Organic& United King, and in Japan of the Japane

ch on the de. :rial refer to a

montmorillo. 67; Granquist. .tands for syn. <right, et a]., made in 1972

Pamphlet as 7f small stacks mets, having an

Of and lis material is lytic cracking,

double-bond nation, and 11 :atalysts and a italysts. As a K-ASYM SMhi in activity be- ic catalvsts. io le, and Product mina catalysis.

CI

n e company's advertising pamphlet indicates it has typical properties as follows:

Appearance: White, free-flowing powder particle size: 2040 micron microspheres Density:

I:.. =- True: 2.5 g per ml Apparent: 0 .w.7 g per mi

- Typical analysis: 48% SiO,

37% ALOs (as received)

2.6% N H o . &., 7 &?. 1.6% F gi,2 12.0% Ha

Trace analysis: 10 ppm Ni 190 ppm Fe 800 ppm Na 100 ppm Ca 250 ppm Mg

0 ppm SO. 1 .

. .

? Surface area: 11C-160 sq m per g, dependent

. Saturationvolume (calcinq 1300°F) N 2 sorption: 0.27 ml per g

on calcination temperature

1 Cation exchange capacity: 1.5-1.6 meq per g Accessible * surface "acidity: 1.8 x 10" sites per g ik;;: * To pyridine vapor at 200°C

il

> Synthetic hectorite is also made in the United Kingdom by Laporte Industries, Ltd., and sold under the brand name Laponite CP (Green, et al., 1970). This material is purer than nat- urally occurring varieties, as it contains, no Rudride. It presumably is suitable for sonk of

-the same uses that synthetic bentonite was developed for in the United States.

' ' For several years an organic-tieated benton- ite has becn on the market under the registered

1 trade name Benlone (Grim, 1962). This . product is processed in such a way that the

original inorganic exchangeable ion on the ben- ! tonite is replaced by an alkyl amine organic

cation. This reaction produces a hydrophobic clay because the inorganic ions that can he hy- drated are removed, and a large part of the clay-mineral surface formerly capable of ad- sorbing water is coated by hydrocarbon chains. Organic-clad bentonites are used in making paint; to gel organic liquids; to produce greases

': having superior properties. for adherence to '' metal, ability to repel water, and resistance to

high temperatures; and in other products. /. - Organic-clad bentonite is also made in the

United Kingdom and France (Anon., 1970) , and in Japan (Takeshi and Kato, 1969). Some : of the Japanese product is sold under the brand

ays 611

name Nikkagel. It is prepared by treating hetonite with alcohol under pressure and heat followed by ion exchange with an organic am- monium salt. A product called Organite is prepared by further exchanging Nikkagel with an amine having a benzene nucleus.

Future Considerations and Trends

The overall demands for both bentonite and fuller's earth seem destined to increase at a rate approximately equal to the growth in Gross Na- tional Product, According to Cooper ( 1970), in the year 2000, production of bentonite in the United States is likely to he three to five times the 1968 amount. The growth rate in fuller's earth requirements will probably exceed the rate forecast for bentonite.

Both bentonite and fuller's earth are used in so many different products and in so many ways that there are many possible substitutes for spe- cific uses, and both have lost markets to other materials in the past. One of the most obvious losses of fuller's earth to other materials oc- curred when the use of synthetic materials in petroleum refining increased before World War 11, and more efficient methods of refining were introduced. Bentonite sales have also suffered mildly from the use of oil-based and speciality muds; however, bentonite is likely to remain the cheapest and most efficient material for mud in certain types of drilling for years to come. Ben- tonite is in some danger of a market loss which may be caused by a breakthrough in the use of another material . for bonding taconite pellets. Though the propostion of bentonite added in taconite bonding is small, it is still a contami- nant, and some type of bonding material that will burn off completely or even add heat in the steel furnace will continue to he sought.

The manufacture of synthetic hectorite and other montmorillonitelike mineral products in the United States and United Kingdom marks a technological breakthrough. Worldwide mar- kets for organic-clad bentonite and washed or otherwise purified white bentonite for speciality products are also likely to increase with general economic growth and the development of new uses and products.

Rising costs of transportation and fuel are two of the major pressures on the bentonite and fuller's earth industries that are likely to have a significant influence on future trends. The cost spread between rail and ocean transportation is the principal reason for the loss to Greek pro- duccrs of some of the Wyoming-type bentonite market for bonding taconite ore in eastern Canada. The comparatively low cost of ocean

.- - 612 Industrial Mine! transportation is also the primary motivation be- hind an overseas search for bentonite reserves near deep water. Progressive increases in fuel costs, particularly for the low-sulfur type re- quired for ecological reasons, seem to be almost a certain forecast. Fuel shortages have caused temporary shutdowns of some plants, and prob- lems related to fuel supply seemed ominous at the time.this article was written.

Kaolin, Ball Clay, Halloysite, and Refractory Clay

Definitions and Classifications Kaolin: The name kaolin is derived from the

Chinese term Kouling meaning high ridge, the name for a hill near Jauchau Fu, China, where the clay was mined centuries ago. Apparently the first to use the name kaolinite for the min- eral of kaolin were Johnson and Blake (1867). The term kaolin is now variously used as a

.clay-mineral group, a rock term (consisting of more than one mineral), an industrial mineral commodity, and interchangeably with the term china clay. The following mineralogical defini- tion by Ross and Kerr ( 193 1 ) is probably the most widely accepted one.

.. By kaolin is understood the rock mass which is composed essentially of a clay material that is low in iron and usually white or nearly white in color. The kaolin-forming clays are hydrous aluminum silicates of approximately the composition 2H,O~AI20,.2SiO1, and it is believed that other bases if present represent impurities or adsorbed materials. Kaolinite is the mineral that characterizes most kaolins, but it and the other kaolin minerals may also occur to a greater or lesser extent in clays and other rocks that are too heterogeneous to be called kaolin.

When applied as a term for an economic clay commodity, the foregoing debi t ion must be modified to include some indication of use and to account for the fact that most kaolin now marketed is beneficiated to improve purity and whiteness. The following definition will ap- ply to further discussions of kaolin in this c h a p ter. Kaolin is a clay consisting of substantially pure kaolinite, or related clay minerals, that is naturally or can be beneficiated to be white. or nearly white, will fire white or nearly white, and is amenable to beneficiation by known methods to make it suitable for use in whiteware, paper, rubber, paint, and similar uses. The term is applied without direct relation to purity of de- posits. Many very large kaolin deposits are

. . L -_._ , ... ,ais and Rocks

essentially pure, and they require little concen- tration during preparation for market. Most are slightly off-color and require bleaching, and others contain as little as 10% clay that must be washed and concentrated to recover market- able kaolin,

China clay is an ancient term originating from the use of clay, later found^ to be ka- olinitic, in porcelain tableware and art objects in China. This term will be used rarely in this chapter.

originating in the United Kingdom many dec- ades ago from the mining practice of prying Out a lump.of clay, rolling it into a crude ball, and loading it into a horse-drawn cart or wagon. Ball clay is defined by the American Society for Testing & Materials (Anon., 1971a) as a secondary clay commonly characterized by the presence of organic matter, high plas- ticity, high dry strength, long vitrification range, and a.'light color when fired. Kaolinite is-the principal mineral constituent of ball clay, and it typically makes up more than 70% of this type of clay. The minor differences between the light fired color required by this definition and the white required for kaolin provide little practical basis for distinguishing these two types of clay. Therefore, ball clay is .actually a variety of kaolin, but it is treated as a separate type of clay because of its wide application in marketing and as a use term in the ceramic industries.

The term ball clay is used in the United States, United Kingdom, India, Republic Of South Africa, and a few other countries. Similar clay or clay used in the same products as ball clay is included with kaolin or china clay in most countries.

Halloysite: Halloysite occurs in t w o " f o k one has the composition (OH),Si,Al,O,;4H&' and the other (OH),Si,AI,O,,. The hydrated form is generally a dense porcelainlike hard clay that dehydrates at surface temperatures Or slightly above to a white or lightsolored porous. friable, or almost cottony-textured maten;?. The dehydrated form is similar to kaolinite 111 composition and mineral structure, and the h y drated form has a c-axis spacing greater than that of kaolinite. The two forms of h a l l o W have caused considerable nomenclature pro! lems. The system most commonly used now IS

to restrict'the name halloysirPto the hydrated form and to call the dehydrated form rnetohol- loysite. However, some reports use the name endellite for the hydrated form and the name halloysire for the dehydrated form. AS Vu-

.

Ball Clay: Baa day is a term apparently ~

.

tually all this the hydrated will be used f

- the mineralog) Halloysite, I

d i n , and it is i duction statist site is acceptec clay industries ologists, and s(

Refractory several varietic in the manufs sistance to higl properties of I

terms of pyro which is a met Pyrometric co number of tha touch the SUI with that of a vestigated, whr Standard Metb Equivalent ( I (ASTM Desig Society for Te

The fusion [ fractory clays

. the lower cutc tions (Norton. (Table 4). TI

TABLE of An

No. of Cons

18 19

20 23 26 27 28 29 30 . 31 32 32% 33 34 36 36 31 38

Originating to be ka.

rely in this art objects

aPParenl1) many dec. of prying

crude ball, 'n c a n or

American ' U 9 7 l a ) aracterized high plar. tion range, :nite is the I clay, and 1% of this :S between : definition ovide littlc these two is actually a separate

application 3e ceramic

he United epublic 01 es. Similar cts as ball na clay in

wo forms:

: hydrated >like hard :ratures or ed porous,

material. aolinite in od the hy- :ater than halloysite ure prob- Led now is : hydrated 1 merahnl- the namc the namc . As vir-

,o,,.~H,o

. . Clays 613

tually all this clay below the surface occurs in olinitic clays are ordinarily classified, according the hydrated form, only the name halloysire to suitability for heat service, as low (PCE 19 to will be used further in this chapter, except in 26), moderate (PCE 26 to 311/2), high (PCE the mineralogy discussion. 31% to 33). and superduty (PCE 33 to 34).

. Halloysite, like ball clay, is a variety of ka- A few essentially pure kaolinite clays have fu- ' ~ d i n , and it is included with kaolin in most pro- sion points as high as cone 35, and some refrac- . duction statistics. However, the term halloy- tory kaolins and fire clays containing diaspore,

site is accepted worldwide, and it is used in the boehmite, or gibbsite have PCEs as high as . clay industries, as well as by mineralogists, ge- .cone 37.

ologists. and soil scientists. The principal types of clay included in the ;; Refractory Clay: Refractory .clay includes refractory clay are fire clay, kaolin. and ball

wveral varieties of kaolinitic clay that are used clay. Definitions of refractory kaolin and re- . in the manufacture of products requiring re- fractory ball clay are the same as given for these - sistance lo high temperatures. The qualities and two types of foregoing definitions, except that ,. properties of refractory clays are expressed in the adjective "refractory" is added to indicate . terms of pyrometric cone equivalents (PCE) use. The definition of fire clay used in this ;"- which is a method of designating fusion points. chapter is essentially the one by Norton (1968). .$ Pyrometric cone equivalent is defined as the which assigns this term to all clays that are not 7 number of that standard cone whose tip would white burning and have a PCE above 19. The ,I touch the supporting plaque simultaneously term fire thy, therefore, excludes most kaolin

with that of a cone of the material being in- and ball clay because they burn white, but it Z vestigated, when tested in accordance with the does include kaolin and ball clay that are co-

Standard Method of Test for Pyrometric Cone lored when fired. This classification of refrac- Equivalent (PCE) of refractory materials tory clay as a group name and the threefold (ASTM Designation C24) of the American subdivision are by no means universally applied. Society for Testing & Materials. Other reports, including earlier ones by the au-

The fusion points of products made from re- thors themselves, have used the terms refrar- fractory clays range from just above PCE 19, tory and fire clay interchangeably. the lower cutoff according to accepted defini-

1.- .. ..

1.

- tions (Norton, 1968), to-as high as cone 37 (Table 4). The refractory properties of ka-

TABLE 4-Tsmperature End Poina

Kaolin

History and Uses: The sedimentary kaolins of the Coastal Plain of Georgia and South Caro- lina and the residual kaolins of North Carolina . ,, .have been known since colonial times. Smith (1929) quotes from Sholes in his chronologi- cal history of Savannah, "1 741-Porcelain Clay

"c was discovered in or near Savannah by Mr. 1490 Duchet, and china cups made." In 1767, Josiah 1520 Wedgwood sent Thomas Griffiths to Macon 1530 County, North Carolina, to send a shipment of 1580 china clay to England (Goff, 1959). Minton 1595 (1922) recorded that, "As early as 1766 Ameri-

can clays from Georgia, Florida, and the Caro- l''' linas were being sent to England in considerable 'Wo quantities." These clays were regularly imported {gi and used by Wedgwood until the clays of En- 1700 gland were available. In 1768 (Barton, 1966). 1725 the English kaolins in Cornwall were discov- 1745 ered, which virtually ended the mining of the 1760 Georgia kaolins for more than a century. In 1785 1876 (Smith, 1929), the mining of the sedimen- i:g tary kaolins of Georgia was started again by

Riverside Mills of Augusta in Richmond County. Mining of the Georgia kaolins has

~~~~~t~~~~ given BpprOXim.f. and Bppii. been continuous since that time. In addition to cable only when heated et rpacifim rates (Norton. the original pottery in Savannah, a second pot-

tery was established near Bath, Aiken County,

_. of American Fyrometric Cones

. ...~

-i ~

:: I ?_ ; .- 4.~.: . .:

.(

I .. .:... . . .. . ..

'. .+< ? ~- ~

614 Industrial Minerals and Rocks !

SC, at an early date. This plant was destroyed .during Sherman's march to the sea (Lang et al., 1940). However. kaolin mining was active again in Aiken County shortly after the Civil War and has continued with only minor inter, ruptions until the present. South Carolina has ranked as the second leading kaolin-producing state for several decades. Kaolin mining in North Carolina started in 1888 in Jackson County (Parker, 1946), and in 1904, the earli- est mines opened in the Spruce Pine district. The first kaolin operation in Vermont (Ogden, 1969) was in the early 18OOs, and most of the product was sold in Troy and Albany, NY.

Production figures for kaolin from most areas in the late 1800s and early 1900s are difficult to trace. It is estimated that about 3 million tons were produced in Georgia before 1932 (Kesler, 19561, after which much better statistics have been available. In 1980, total production in Georgia alone was over 6 million tons, and South Carolina ranking second produced more than 657 thousand tons.

Kaolin has many industrial applications (Murray, 1963a), and new uses are still being discovered. It is a unique industrial mineral be- cause it is chemically inert over a relatively wide pH range, is white, has good covering or hiding power when used as a pigment or extender in coated films and filling applications, is soft and nonabrasive, has low conductivity of heat and electricity, and costs less than most materials with which it competes. Some uses of kaolin require very rigid specifications including particle-size distribution, color and brightness, and viscosity, whereas, other uses require prac- tically no specifications: for example, in cement, where the chemical composition is .most im- portant. The better grades of kaolin make up most of the tonnage sold and, of course, have the highest value. Many grades of kaolin are specially designed for specific uses, in particu- lar for paper, paint, rubber, plastics, and ceramics.

The paper industry is by far the leading con- sumer of kaolin (Fig. 7), and approximately 50% of the tOLdl production is used in paper products. Much of the paper used in today's color picture magazines contains as much as 30% by weight of kaolin. Kaolin used in paper fil ls the interstices of the sheet and coats the surface, imparting smoothness, gloss, brightness, opacity, and printability (Bundy, et al., 1965). Kaolin is less expensive than paper pulp and thereby effectively lowers paper-production costs, and it is cheaper or more efficient than other materials used in filling and coating. It is

inert to the other ingredients in paper, is R- tained well between the paper fibers, is avail. able in large quantity, and the platy structure of kaolinite lends itself to the production of high-gloss papers. The low viscosity of kaolin at both high and low shear rates is a very important property, because at today's very high speed production rates the coating must be a p plied at high solids content and still give the correct coating thickness and opacity to the paper. High-quality paper coating kaolin flows readily when applied with very high speedcoat- ing equipment, giving the paper a smooth and even film. : .

The rubber industry uses large tonnages of kaolin as a filler or extender in both natural and synthetic rubber (Fig. 7). Kaolin is incorpo- rated in the latex mix to improve properties such as strength, abrasion resistance;-and ri- gidity; furthermore, it lowers the cost. Through the years, two terms, "hard-kaolins" and "soft- kaolins" (Klinefelter et al., 1943), have bkorne commonplace in describing types of kaolin used by the rubber industry. The hard kaolin, though distinctly softer than flint kaolin or flint clay. is a very fine particle-size kaolin that tends to im- prove the tensile strength of rubber and its re- sistance to tear and abrasion. The principal products in which large quantities of the hard varieties are used are footwear and cable coven. Soft kaolin lacks the reinforcing properties Of the hard kaolins and is used to lower elasticity and improve abrasion resistance, particularly in such products as floor tile and soft rubber goods. : .

Kaolin is used as an extender in paints cause it is chemically inert, has a high covering power, gives desirable flow properties, is low In cost, is white, and reduces the amount of pensive pigment required. In addition, it has very excellent suspensioii properties and, 1s available in a wide range of particle sizes which can be used in many types of paints. For.ex- ample, coarse-particle kaolins are used in paints where a dull o r flat finish is required, and fi"'- particle kaolins are used in high-gloss paints. Large quantities of calcined kaolin and, Water- , beneficiated kaolin are used in interior Rat wall paints and in metal primers, Water-beneficiated grades of kaolin disperse easily in water and are, therefore, particularly suited to latex pain's. Some kaolin is chemically treated to rnake,it organophilic or hydrophobic and thereby is sur'. able for use in exterior oil-base paints. Calcined kaolin, because of its resistance to abrasion and dry covering properties, is being used in increa5- ingly large quantities by paint manufactoren.

Y) E O c c

& 2= In U c 0 In 0 a

5 - 'Z -I 0 Q Y

FIG.

;.. ..

Calcined kaol TiO?, the lead. latex types, ac plifies the forn

Kaolin is u: tics. The desir

. s~ l t ing from t1 surfaces. mor< stability, and Manufacturers kaolin as a rei plastic more .

~ calcined kaolii insulation to j

manufacturing ]in has helped hindered prod automobile b, kaolin actual11 form pari o r b future growth

1. -. - -_ ~. - .. . . . . .. .. .

Clays 615

in paper, is *. ,*'. fibers, is avail. $5:.

: platy structure 2 Production of

,cositY of kaolin rates is a VCQ

Today's very hiF), ring must be ap, nd still give th

opacity to tk Ling kaolin nou, high speed coat.

2r a smooth artd

irge tonnages O !

both natural ani! aolin is incorpr,. ?we Propertic, ;:stance, a ld ti. le COSt. Throush dins" and "w:. 3 1. have becorn; 2s of kaolin u ~ r t .d kaolin. though n or flint clay. I, that tends to inr- .tbber and its rc.

The princip:rl ities of the bil! 3nd cable c o w \ ng propertie5 nl

3 lower elasiici:? 'e. particularly 11:

m d soft rubk ;

ler in paintr~hc-

In c 0 c c L 0 I In U E 0 In 3 0 f - z -I 0

Y

-

a

8.000

7,000

6,000

5,000

4,'000

3,000

2,000

I,000

0 1965 1967 1969 1971 1973 1975 1977 1979 1981

YEAR

FIG. 7-Kaolin sold or used by domestic producers for specified uses (Ampian, 1980, 1983).

.. ~. ,. I a high COVCIIII; mperties, is low :TI

f amount of c \ . addition. i t h3,

openies 3nd i\ rticle sizes which paints. For cs.

(re used in paint. quired, and finr- tigh-gloss paint\ 3oIin and water.

interior flat u.311 ater-beneficiald ly in water 2nd d to latex paint\ ated to makc i t d thereby is si l i l . paints. CalcinrJ to abrasion nnJ

;used in increai- manufactiircr'.

Calcined kaolin is an excellent extender for i TiO?, the leading paint pigment, particularly in *. latex types, and its use reduces costs and sim- * plifies the formulation of the paint.

Kaolin is used extensively as a filler in plas- a tics. The desirable characteristics in plastics re- sulting from the use of kaolin include smoother surfaces. more attractive finishes, dimensional ; stability, and resistance to chemical attack. f Manufacturers of polyvinyl chloride (PVC) use

kaolin as a reinforcing agent, and it makes the 5 plastic mori durable. Calcined and partially $ calcined kaolins are used as a filler in PVC wire

insulation to improve electrical resistivity. ' I n 5. manufacturing glass-reinforced polyesters, kao-

lin has helped eliminate flow problems which hindered production of large products, such as automobile body parts and boat hulls. The kaolin actually results in a stronger, more uni- __ form part or body. Plastics are a major area of

I

.'

future-' growth for kaolin products. They are

used extensively in vinyl floor coverings, and surface-modified kaolin gives improved dispersi- bility in certain plastic systems, which will greatly increase their usage.

Historically, kaolin was first used in ceramics, and this is perhaps still the best knobn applica- tion, even though the total tonnage sold for this use is small compared with that marketed for paper, paint, and rubber manufacturing (Fig. 7 ) . It is used in the manufacture of whitewares, wall tile, insulators, refractories, and in some face brick when a white color is desired. Spe- cially designed grades with high green and dry strengths are available for use by whiteware manufacturers. The most important properties for this use are plasticity, strength. and fired color, Kaolin is used in insulators because of its properties of low conductivity, high dielec- tric constant, low power loss, plasticity, and fired strength. Kaolin is used in casting opera- tions because of its excellent flowability, sus-

- -.

.. 616 Industrial Minerals and Rocks

pension properties, color, and water-release characteristics. Kaolin is also used in porce- lain, again because of its excellent suspension characteristics and good color.

Kaolin has many other important applica- tions, but in terms of tonnages required com- pared with the aforementioned uses, they are rather'small. Although the following list is not complete, it gives an idea of the extremely wide range of products containing kaolin as a sus- pending agent, filler, extending agent, or a main constituent because of its chemical or mineral composition, whiteness, particle size, or other properties:

.. f

ing particle size and particle-size distribution are used, hut the most accurate is based on the Stokes principle. Size determinations can be. made by the application of this principle, be- cause settling rates in fluids are controlled by particle diameters when the attraction-of grav- ity, densities of particles and fiuids, shape of particles, and the viscosity of the fluids are identical. Coarse particles, therefore, settle more rapidly than finer ones, and determina-

can be made by the time-rate principle. The

I ,

: .

tions of a given particle size and distribution

time-rate principle is equally valid for settling by gravity or when settling is auemented hv

c

u u

ink adhesives insecticides medicines food additives catalyst preparations bleaching adsorbents

cement fertilizers plaster filler aids cosmetics chemicals crayons pencils detergents

porcelain enamels paste roofing granules sizing foundries linoleum floor tiles textiles

Production Specifications: Paper Filler and Coater-The most important specifications for kaolin used in paper applications are bright- ness, particle size and particle-size distribution, viscosity, and screen residue. Some purchasers also require tests of abrasiveness. The Techni- cal Association of the Pulp and Paper Industry [TAPPII (Lyons, 1966) has given detailed in- formation regarding the properties and test pro- cedures for kaolin used in paper, and only brief descriptions of the more important tests will be outlined.

BRIGHTNESS-This test consists of drying, pulverizing, forming a plaque, comparing with a standard of known brightness, and calculating the brightness measured at 457 millimicrons with a reflectance meter constructed. calibrated.

I

and operated according to the requirements of The Technical Association of the Pula and Paper Industry Standard T452M-48. TGs test must be very carefully done by an experienced and competent technician in order to obtain accurate and reproducible results. In general, a minimum brightness of 80% is required for filler clay and 85% for coating clays.

PARTICLE Sm.-Many methods of determin-

centrifugation. A rapid t ea for $ant control ~I

consists of the preparation of a standard, dilute deflocculated slip of the clay in question, set- tling by controlled centrifugal force for pre- determined short-time intervals under such con- ditions as.to effect reproducible packing of the sediment, and measuring the apparent volume bf sddiment at each time interval. Tmical

0 I W .I particle-size analyses of filler and coating grades are shown on Fig. 8. FIG. 8-(

VISCOSITY-FIOW properties of kaolin are very important to the paper coater because they affect the functioning of the coating operation as well as the final quality of the paper product: TWO viscosity tests are used in the kaolin indus- try, one to measure high shear viscosity and the other to measure low shear viscosity. The mea- surements are generally made on slurry suspen-~ sions at 71% solids. A Brookfield fourspeed viscometer is used to measure low shear vis- cosity. A Hercules viscometer is used to mea- sure high shear viscosity. Standard procedures and conditions are rigorously followed in mak- ing these tests.

SCREEN RESIDUE-Material held on a 325- mesh screen is regarded as grit or residue. A 100% sample is thoroughly mixed and dispersed with a dispersing chemical. After carefully de- termining the weight and percent solids of the dispersed slip, the amount of residue retained on the screens can be accurately weighed and percentages calculated.

Filler ,for Paint and Plarrics-In addifion 10 several of the properties required for use in paper, the kaolin used in paint and plastics must meet certain electrical resistivity specifications. The resistivity test is designed to give an indica-' tion of the amount of ,residual salts that might be contained in the clay. The higher resistivity values reflect a low soluble-salt content. A cer- tain Weight of kaolin is added to a specified weight of distilled water. The suspension is boiled for 5 min and reweighed. The loss of

'

distilled water conductivity ii conductivity b

For certain fineness-of-gril This test is in dispersion (A fineness gage brated from 0 by numbers. the particles ar paint customel tender must b< number.'

Ceramics-' olin sold for c rupture, castin lent (PCE), f measurement basic requirem modulus of ,- strength of a The MOR me; Of either recta supported neai central part of standard methc

Casting ratc hoilies cast mc cosity of a slip if it is too visc the mold or d,

-

. . , . .

Clays

-.

617

j of kaolin atr fter becaucc the! oating operation le paper prddili: the kaolin indu.. viscosity and ihc :osily. The mrj. in slurry s u s p c ~ <field f o u r - r p d z low shear vi\. is used IO m c ~ .

idard procediirm 'ollowed in mal.

held on a 325. it or residue. A ed and dispencd 'fer carefully dc. cnt solids of thc residue retained ely weighed and

-In addition tc iired for use in and plastics must ty specifications. o give an indica- salts that mi@

higher resirtivilY content. A Ccr-

d IO a specified le suspension i s

,ed. The loss Of

For certain paint applications, the Hegman i fineness-of-grind test specification is important. I This test is intended to measure the degree of

dispersion (Anon., 1 9 7 0 ~ ) and conskts of a fineness gage and a scraper. The gage is cali-

-. brated from 0 IO 8, and the fineness is reported by humbers. The higher the number, the dner

$.the particles and the better the dispersion. Some paint customers specify that a pigment or ex- tender must be finer than a particular Hegman

Ceramics-The most important tests for ka- -olin sold for ceramic products are modulus of

e mold or drain cleanly. Therefore; viscosity

is measured and controlled on shipments of kaolin used in the casting process.

For certain applications, particularly for re- fractory purposes, the pyrometric cone equiva- lent (PCE) is measured. The pyrometric cone measures the combined effects of temperature and time (Anon., 1952: Klinefelter and Hamlin, 1957; Norton, 1968). The cones consist of a series of standardized unfired ceramic composi- tions molded into'the shape of triangular pyra- mids. The sample of kaolin is molded into the standard cone shape and is heated along with several standard cones so that its end point can he determined in terms of an equivalent cone number. ASTM test method C24-56 gives the procedure of making this PCE test (see Table 4)-.

The fired color of kaolin is also important because some burns white and some burns buff or slightly pink. This is a visual test, and the test specimen, fired to a predetermined tem- perature, is compared with a standard.

Shrinkage is an important property. Ceramic articles undergo shrinkage at several different points in the manufacturing sequence. During drying, the article will shrink in varying amounts depending upon its composition and the amount of water present. The article shrinks further during firing. Therefore, it is important to know both the drying shrinkage and the firing shrinkage. Linear shrinkage and volume shrinkage can both be measured, al-

,*. - ,

1 . . . , - . - Industrial Minerals and Rocks

. . , '

though linear shrinkage is more commonly reported (Jones and Berard, 1972).

Miscellaneous Uses and Producrs-Because of the many different uses of kaolin, the in- dustry is plagued by many different purchase specifications and product requirements. Vir- tually none of these, except those outlined in foregoing discussions, have been. standardized, and purchase specifications are frequently changed. However, the grades of kaolin now marketed by the major producers, those grades described in sales and advertising brochures, can, with or without blending, fulfill a wide variety of specifications.

Geology: Mineralogy-By definitions, the clays discussed in this section consist chiefly of kaolin-group minerals. The members of this group.are kaolinite, nacrite, dickite, and halloy- site. With the exception of the hydrated form of halloysite. which has somewhat more water. all these minerals have essentially the. same composition. Their overall crystal structures are also similar, but minor differences in ar- rangements of ions in octahedral positions, stacking of unit layers, crystal habit, etc., are sufficient to cause the use of separate names. Kaolinite is, of course, the most common mem- ber of the group, and halloysite obviously forms halloysite deposits. The other two members of the group rarely occur in economic deposits.

Structurally, kaolinite consists of an alumina octahedral sheet and a silica tetrahedral sheet. These sheets form triclinic crystals. The theo- retical structure formula of kaolinite is (OH),- Si,AI,O,,, and the theoretical composition is S O , 46.54%, AI,O, 39.5%, and H,O 13.96%. There is relatively little ionic substitution in the mineral lattice, although there is evidence sug- gesting minor substitution of iron for aluminum in some kaolinite. The perfection or degree of ordering of kaolinite crystals varies consider- ably. By interpretation of X-ray diffraction data, Murray and Lyons (1956) have shown that the crystallinity of Georgia kaolin ranges from poorly ordered to very well ordered forms. Other investigators (Brindley and Robinson, 1946; Range, et al., 1969) have found similar variations in ordering in kaolinite from several localities. The more perfectly ordered forms of kaolinite commonly occur in hexagonal or sub- hexagonal crystals. Growths of crystals along the c-axis into accordionlike or vermicular forms are also common. Fig. 9 is an electron micrograph which shows both the hexagonal thin plates and vermicular stacks of kaolinite.

The clays described i n this section contain. in their natural occurrence:a wide variety of min-

era1 impurities. Georgia kaolin generally is 8s . .

to 95% kaolinite, the remainder is mainly j quartz, minor muscovite, biotite, smectite, ilmenite, anatase, rutile, leucoxene, goethite, and traces of zircon, tourmaline, kyanite, and graphite. Kaolin deposits in Latah County, Idaho, contain considerable ilmenite (Hoster. man et al., 1960). Kaolinite and halloysite make up from 10 to 40% of residual deposits in the Spruce Pine district, North Carolina. The bulk of these deposits consists of aneular auartz.

- ,

:

.- . ~~. muscovite, microcline, and partly aliered plagi- C h e (Parker, 1946). The well-known English kaolins, which are I O to 40% kaolinite, consist mainly of quartz, mica, and potash feldspar: tourmaline is also present (Bristow, 1969).

Occurrence-Most kaolin is soft and plastic when natural moisture is presenttor where wa- ter has been added to dried material:--One way of describing the natural texture is by the col- loqujal .phrase-a good whittling clay-which refers to the ease with which the clay can* carved with a knife. Dry kaolin is ordinarily friable, and a common but not a diagnostic test fo r i t is its stickiness when touched to the tongue. Some types of kaolin, which have a p parently been under considerable overburden or which contain introduced silica, are hard and are sometimes referred to as flint -kaolin. Though much more lithified than plastic varie- ties, this so-called flint kaolin is softer than most flint clay referred to in the sec:ion cn fire Clay. which also consists of kaolinite.

Kaolin and related clays occur in several djf- ferent types of deposits. Many kaolin deposlu throughout the world are in the form of tabular lenses and discontinuous beds in sedimentar). rock. Most deposits of this type are of ere- taceous age or younger. The shapes and lateral extent of such deposits vary appreciably. D,c' posits as much as 60 f t thick are common In

some districts. and bodies of kaolin are known to extend laterally for more than a mile. Ex. tensive sedimentary deposits of this type Occur in the Georgia-South Carolina kaolin belt (Anon., 1970i), Arkansas bauxite region (60:- don, et al:, 1958), and Ione district, California (Johnson and Ricker, 1948) [Fig. IO].

Residual kaolin deposits occur in weathered rock, and they are at or very near the surface. except where they formed during ancient wea- thering cycles and were later buried hy Younger rocks. Most residual kaolin deposits have formed from igneous rock. The age of kaolin formation is commonly controlled by the age Of

the present land surface rather than the age Of the parent rock. Residual kaolin deposits arc

"

FIG. 9-& Georgia kaoli thin p/ates ai

of

.. - . , - .

'.

generally "iiregul ward into the p tered weathered commonly 'cont: regular masses c rock that were o blocks or otheru water. Residual Spruce Pine dis! 1946); the Arka et al., 1958); 1 and Keller. 196 nia (Cleveland, United States ' ( I many other cour mon in Czecho: Brazil (de Souz: 1972).

Some kaolin Occur in rocks I

'ne:ally is X J IS mainl!

smectitc, ne. GOethitr, kyanite, an,, .tab Count!. lite ( H O ~ I ~ , . nd halloysit: dual deposil, 3arolina. Th: 'gular quartz. hered plapi,,. .'own Engli\h linite, con\i\t :ash feldspar: )W, 1969). >ft and pla\t,,. %where u;,.

:tal. One w3, is by the cni. : clay-whirl, e clay can hc 1 is ordinarii) diagnostic IC\:

,uched to i t l r ,hich have ap. overburden are hard 2nd flint kaohn

I plastic v a r ! ~ . mfter than nit>,: n on fire cl:~;..

in several di!. :aolin depouh arm of tahit!:;; n sediment:!:) e are of C:: pes and latc::tl ireciahi!'. I X ;e comni(rn 1 8 )

,din are knoun n a mile. I.*- his type ozil i: a kaolin IKL e region (Cic>i- .ict. California g. 101. I in weathere? ar the s u r f a x g ancient wcil. ied by yOUn?C' deposits h ~ c

d by the age han the a s 0:

deposils arc

age of kaoli?

FIG. 9-Electron micrograph of Georgia kaolin showing hexagonal thin plates and vermicular forms

of kaolinite. .

. _. . .- .- . . . . . . . .. .

Clays 619

- generally irregularly shaped and grade down- : ward into the parent rock through partly al- j_ tered weathered saprolite zones. They also - ,

commonly contain iounded boulders and ir- = regular masses of fresh or only partly altered E rock that were originally in the centers of joint

blocks or otherwise'protected from percolating 5. water. Residual kaolin deposits occur in the P Spruce Pine district. North Carolina (Parker, s Y 1946); the Arkansas bauxite district (Gordon, g e t al., 1958): Latah County, Idaho (Ponder

and Keller, 1960); Alberhill district, Califor- E nia (Cleveland, 1957); and elsewhere in the

United States (Fig. IO). They also occur in 9- !.:many other countries and are particularly com- E mon in Czechoslovakia (Kuzvart, 1969) and 'i Brazil (de Souza Santos and de Souza Santos,

_.

1972).

altered. Such deposits are ordinarily in irregu- larly elongate pods or pipelike bodies aligned along joints. faults, or other permeable zones that allowed movement of warm or hot aqueous solutions. Some deposits of this type also occur in altered tuffs and are bedded. As with the re- sidual type, the age of hydrothermal kaolin for- mation is not necessarily related to the age of the host rock. Most hydrothermal clay deposits are probably no older than Tertiary, though some occur in rocks that are much older. Inso- far as the authors are aware, deposits in the Little Antelope Valley, California (Cleveland, 1957), contain the only hydrothermal kaolin now mined in the United States. It is used for refractory clay. However, kaolin formed by this process occurs at many places in the western states, and deposits were formerly mined on a small scale in several mining districts.

Origin-The two fundamental geologic proc- .

620 - _

Industrial Minerals and Rocks

+ Producing d11tric1 I,

d Ma@ repion

A PrOducinp district A Minor or inaclive dirtlid +- Minor 01 inactin diivCl

BALL CLAY REFRACTORY CLAY a 500 M~IS - Producing district Producing district

0 Mi- w inactin dirtrkt 0 Mina a inxtw district .. _- FIG. 10-Map showing kaolin, ball clay, halloysite, and refractory c/oy disfricts in the US.

esses that form most of the clay minerals of the kaolin group are weathering (Keller, 1964) and hydrothermal alteration (Sales and Meyer, 1949). These processes under certain condi- tions remove elements other than silicon, alumi- num, oxygen, and hydrogen, the constituents of these clays. The clays form as the other ele- ments are removed from preexisting minerals and possibly by the growth of new atomic ar- rangements from materials in solution. Though most kaolin minerals form in these ways, the origin of valuable deposits is quite another mat- ter. Certainly several commercial clay deposits throughout the world have formed by hydro- thermal processes, and others have formed in place by the weathering of other rocks. How- ever, many of the large high-grade deposits of kaolin occur in sedimentary rocks and have either been (1 ) transported and deposited as kaolin; (2) altered from previously transported mcks by processes related to surficial weatber- ing, submarine or subaqueous alteration, or posthurial (diagenetic) changes; or (3) com- binations of these possibilities.

Knowledge regarding the origin ofkaolin de- posits in the United States varies considerably. The origins of some of the deposits are reason- ably well established, but geologists have widely differing opinions on how other deposits formed. Clearly, many of the scattered ka- olins in western states formed by hydrothemla1 processes, hut few such deposits have been Slg- nificant sources of kaolin. In the Arkansa bauxite region (Gordon, et al., 1958) and in Latah County, Idaho (Hosterman, et a l . 9

1960), are districts containing both tram- ported clay and residual kaolin formed, by weathering of igneous rock. In both distn?? the kaolin grades downward through saprol!llc zones into parent rock, which is nepheline syenite in Arkansas and granodiorite in Idaho. Also, in both districts, kaolin transported from the residual material occurs in sedimenta? rocks-in marine shale in Arkansas and In lacustrine beds in Idaho. However, this ex- planation of origin is inadequate to account for all the kaolinitic clays in the regions con(a1nlnK these districts. The transported kaolin in AI-

.. kansas is of Wilc kaolinitic clay 01

throughout a muc; can be related to

- kansas. Similarly, cannot all be relat type of kaolin del understood occurs Valley and Ridge of the United Stat parently formed by nous minerals by sinkholes. Probabl terials were mainly of carbonate rock. based on the pre: bauxite in the cent, enclosing envelope the kaolin from the of the sinkholes.

Strange as it ma origins are least unr extensive belt in G which have been stu mineralogists and %

source of commerci have investigated th, the kaolin or the mi has been transportt center about expla large deposits of f i r have formed in en sediments being dc containing much ms Furthermore an ad? Of the deposits mus facts: (1) some d grained than others dant accordionlike j

(3 ) gihbsite is prese in others; (4) ligni. organic matter are and ( 5 ) smectite is variable quantities.

One of the first gl gia kaolin was by 1 the deposits but dit Veatch (1909) con member of the Crc loosa, is the most im tion in Georgia. I+ the formation in G~ by its stratigraphic that the material n Formation was de'ri, decomposed rocks The greater pan of

- !

i in the US.

of kaolin de- considerably. LS are reason- :shave widely .her deposit: scattered ka- hydrothermal lave been sig- the Arkansas 1958) and in man, et al..

both trans- 1 formed by both districts. ugh saprolitic is nepheline

,rite in Idaho. ,sported from

sedimentan dnsas and in ever, this ex- to account for Ins containing kaolin. in AT-

p"" I

.

Clays

kansas is of Wilcox age (early Eocene), and kaolinitic clay occurs in rocks of this age throughout a much more extensive region than can be related to the nepheline syenite in Ar- kansas. Similarly, the Miocene clays in Idaho cannot all be related to granodiorite. Another type of kaolin deposit that is reasonably well understood occurs as sinkhole fillings in the valley an$ Ridge province in the eastern part of the United States. This type of kaolin ap- parently formed by the leaching of other alumi- nous minerals by downward-moving water in sinkholes., Probably the parent aluminous ma- terials were mainly residuum from the solution of carbonate rock. This explanation is in part based on the presence of cores of gihbsitic bauxite in the centers of such deposits and the enclosing envelopes of cherty clay separating the kaolin from the carbonate rock in the walls of the sinkholes.

Strange as it may seem, the deposits whose origins are least understood include those in the extensive belt in Georgia and South Carolina which have been studied by many geologists and mineralogists and which lead the world as a source of commercial kaolin. Virtually all who have investigated these deposits agree that either the kaolin or the material from which it formed has been transported. Areas of disagreement center about explanations of how such very large deposits of fine-grained white clay could have formed in environments in which some sediments being deposited consisted of sand containing much more iron than does the clay. Furthermore an adequate explanation of origin of the deposits must account for the followhg

-facts: ( I ) some deposits of kaolin are finer grained than others; (2) some contain abun- dant accordionlike booklets and some do not; (3) gibbsite is present in some deposits and not in others; (4) lignitic layers or layers rich in organic matter are present in some deposits: and ( 5 ) smectite is present in some deposits in variable quantities.

One of the first geologic studies of the Geor- gia kaolin was by Ladd (1898); he described the deposits but did not discuss their origin. Veatch (1909) concluded that the lowermost member of the Cretaceous system, the Tusca- loosa, is the most important clay-bearing forma- tion in Georgia. He indicated that the age of the formation in Georgia was determined only by its stratigraphic position. Veatch believed that the material making up the Tuscaloosa Formation was derived from disintegrated~and decomposed rocks of the Piedmont Plateau.

.Tb? greater part of the Piedmont region was a

land surface for a very long period of geologic time. Just before the beginning of the Cre- taceous, the Piedmont region was uplifted and tilted southeast, Streams rapidly carried the weathered residue to the Cretaceous sea. Veatch postulated that an enormous quantity of sedi- ment was dumped rapidly at the stream mouths. forming extensive sand flats. Fine clay parti- cles were deposited in nonpersistent and lenticu- lar beds of white clay in the deeper and quieter waters near the stream mouths. He considered the Tuscaloosa in Georgia a nonmarine deposit.

Smith (1929) concluded that the basal Cre- taceous sediments in Georgia were Upper Cre- taceous and correlated them with the Midden- dorf Formation of eastern South Carolina. Smith believed that Veatchs explanation of origin was essentially correct, except that he agreed with Neumann (1927) that the kaolin was deposited in saltwater. Cooke (1943) assigned the basal Cretaceous sediments to the Upper Cretaceous under the name Tuscaloosa. which is st i l l used. Kesler (1963) believes that in east-central Georgia there is no basis for sub- dividing the Upper Cretaceous, and he found that the kaolin lenses have no preferred strati- graphic position within the formation. Kesler theorized that feldspathic sands were deposited as delta sediments above sea level and were subsequently altered to kaolin. The kaolin was separated from the coarser sediment and de- posited at p i n t s of lowest elevation. As the kaolin accumulated in the ponds, sand was washed from the margin into and over the edge of each deposit, forming gradational and inter.. fingering contacts.

Bates (1964) reviewed the origin of the Georgia kaolins and summarized the minera- logic and geologic data, some of which support a marine origin and some a freshwater origin. Hinckley (1961) suggested that face-to-face flocculation of kaolin particles in a marine en- vironment would result in the properties that distinguish a so-called "hard" kaolin, whereas edge-to-face flocculation in freshwater would produce a less dense, "soft" clay. Buie (1964) proposed the possibility that volcanic ash was first altered, to montmorillonite and then to ka- olinite. This is a radical departure from pre- viously proposed theories of origin, and much more detailed field and laboratory work must be done before this hypothesis can be ade- quately tested. Jonas (1964) concluded from a detailed petrologic study that .the originally deposited sediment was muscovite, feldspar, and quartz, and that postdepositional alteration and

622

recrystallization produced the kaolin deposits now mined.

Recent studies of spores, pollen, and inverte- brate fossils in and associated with kaolin indi- cate that many of the deposits thought to be Cretaceous are of Eocene age (Buie and Foun- tain, 1967; Cousminer and Terris, 1972; Scru- dato, 1969). a possibility suggested by Eargle (1955). The first announcement of the Eocene age for any of the deposits was by Buie and Fountain, who on the basis of paleontological evidence established the presence of middle Eo-

' ' cene strata beneath some. of the commercial kaolin deposits and above others. In one of the studies, Cousminer and Terris (1972) con- cluded through palynological work that some, if not all, of the sedimentary kaolin is middle Eocene in age. Results of palynological studies by R. H. Tschudy of the US Geological Sur- vey on samples collected by Patterson have con- firmed that some of the kaolin deposits are of Late Cretaceous age or older, and that some are no older than Claiborne (middle Eocene), Tschudy's work also revealed that sand beds of Paleocene age are present in the kaolin belt. This raises the possibility that some of the ka- olin deposits may be of Paleocene age and that kaolin deposition took place during several

taceous in age contain more vermicular crystal growths and coarser particles than do the de.

Major Kaolin-Producing Countries: United States-GEORGIA-SOlJTH CAROLINA KAOLIN BELT-The principal reserves and the major kaolin-producing centers in the United States are in a belt extending from Twig@ County in the central part of Georgia to Lexington County in west-central South Carolina. 'This same bell extends southwest from Macon to Anderson. ville, G A (Zapp, 1965), and west to Eufaula. AL (Warren and Clark. 1965). The Anderson- ville and Eufaula districts contain appreciable kaolin resources, but both are centers of p r a duction of refractory kaolin. and refractory bauxitic materials, and no kaolin, as defined in this report, is now produced in either district.

The deposits in the Georgia-South Carolina belt occur in sedimentary rocks a short distance seaward.from the crystalline rocks of the Pied. mont'region. The major mining and beneficia- tion activities are in Twiggs, Wilkinson, and Washington Counties, Georgia, and in the vi- cinity of Aiken, SC. Large reserves of fine- particle-size kaolin have been discovered in the last 10 to 15 years in the vicinitv of Wrens, GA.

posits known to be of Eocene age. . .

~~~ ~~

I.

IDAH-Filler. ficiated in Latah its occur as re2 granodiorite and terman, et al., 19 Mineralogical an deposits contain I ite and that the c ing almost all 1 kaolin, quartz, i quantities of othc

NORTH CAROLI : . . mary kaolin (the

here as cornmonl: ' try for hydrother,

sidual deposits c weathering) alteri (Parker, 1946) is kaolin is a mixtui and i s used prima These deposits ger 40% kaolin and quartz, hornblende removed by wet b duce a usable prod

TEXAS-Near K of earlv Eocene P

A

~ ~. which is in the eastsentral part of the. belt.

'- Other reserves are scattered throughout the bdt. mined k d benefic clav (Fisher et al. different intervals of geologic time.

The recent findings on the range in age of Georgia kaolin deposits reinforce our opinion that the deposits have had a very complex his- tory and origin, and the theories advanced to date do not provide adequate explanations. Probably the purity of the kaolin is the result of some sedimentary winnowing process, an idea favored by Kesler (1963) and others, as evidence now available suggests that the ulti- mate source was aluminum silicate minerals in the crystalline rocks to the northwest. The en- vironment in which the deposition took place is yet to be established, but it was probably simi- lar to the present coast of Georgia and South Carolina. where there are abundant offshore sand bars and swampy, muddy lagoons and winding estuaries. How iron was removed from the kaolin remains a problem; removal of iron may have been due mainly to chelating by or- ganic acids from decaying plant materials, and oxidizing pyrite may have contributed to the process. Some of the differences in physical properties of the kaolin may be due to the fact that parts of the deposits, particularly the younger ones, have been reworked. Other dif- ferences in physical properties are probably due to varying degrees of diagenetic alteration, as most of the deposits now known to he Cre-

Very large potential resources of off-color hi@ iron clay and deposits under overburden that IS

too thick to be stripped profitably, at present. are scattered throughout the seaward parts Of the belt.

ALABAMA-Kaolin is mined from the Tusca- loosa Group in Marion County, Alabama (Clarke, 1964). It has been mined in this area for 40 years, and approximately 1 million tons has been shipped. This kaolin is relatively Pure and is easily beneficiated by removing qUan.2 and mica. Most of the production from this district has gone into various ceramic producls.

CALIFORNIA-Filler-type kaolin is mined and processed near lone and Bishop, CA. The lone clay is sedimentary <n origin (Bates, 1945). whereas the kaolin near Bishop is hydrothermal (Cleveland, 1957).

F L O R I D A - T ~ ~ Florida kaolin is found in sand and gravel deposits of the Citronelle For- mation (Calver, 1949). The formation ranges from 20 to 55 f t in thickness, and the recover- able kaolin averages about 15%. The only 09 erating mine is in Putnam County. Most Qf the production is sold to the ceramic industry. Re- cently, these kaolinite sediments were named the Fort Preston Formation and dated middle Miocene (Calver, 1949).

- .- ,

,

~ ~ ~ . . scribed these depo They contain 40 to is a byproduct of a

OTHER STATES- the. past or has bec mercial quantities i Illinois (Grim, I ? 1970), Mississipp Mexico (Glassmire 1969), and Virgi 1920).

R ESOURCES-R~S United States of a than the lower gra least 1 billion tons. about which there supply is the very 1 white clay suitable certain other speciai serves of this type o 200 million tons, P, including discolorec' that below more ove ably stripped at pre estimated reserves.

Unired Kingdoln. second only to the 1 Of kaolin or china

nicular cvsta1 an do the dr.

ntries: u n i l r d JNA KAOLIX !nd the majoi United Stath

kgs County in +ton Count! This same bell $0 Anderson.

:St to Eufau!l, The Anderson. :In appreciabk :enters of pro. ind refrlctor, 1, aS defined in either district. iouth Caro:!ni short dirlancc

ks of the Pied. and beneficia.

Vilkinson, atad and in the W .

serves of f in<. ;covered i n thc of Wrens, G.A. rt of the hr\i ighout the hcl! off-color h i g h rburden that I, ily, at prexn:. %ward pan3 o!

'om the TILSC:~. nty, Alah:arwb led in this arc3

1 million ICII!~

relatively pikx moving qwf:! tion from t! i~< ilmic product, n is mined 21::

CA. The 1 0 1 ~

:Bates, 19J!i. ; hydrotherm.1!

n is found In Zitronelle FCI. .mation r a n p Id the recoYcI.

The only OP y, Most of Ihc industry. Kc. were n m c J

I dated midJic

_.

I=- . , . . - . . .- ..

Clays 623 IDAHo--Fil!er-type kaolin is mined and bene.

ficiated in Latah County, Idaho. These depos- its occur as residual weathered products of granodiorite and as lacustrine sediments (Hos- terman, et al., 1960 Ponder and Keller, 1960). Mineralogical analyses show that some of the deposits contain halloysite in addition to kaolin- ite and that the deposits are variable, some be- ing almast all kaolin and others containing kaolin, quartz, orthoclase, mica, and minor quantities of other minerals.

NORTH CAROLINA-Near Spruce Pine, a pri- mary kaolin (the term primary kaolin is used here as commonly applied in the kaolin indus- try for hydrothermal-type deposits and for re- sidual deposits of kaolin formed by in-situ weathering) altered from pegmatite and aplite (Parker, 1946) is mined and beneficiated. This kaolin is a mixture of kaolinite and halloysite and is used primarily by the ceramic industry. These deposits generally contain approximately 40% kaolin and halloysite, so that the mica, quartz, hornblende, and other minerals must be removed by wet beneficiation methods to pro- duce a usable product.

TEXAS-Near Kosse, Texas, a kaolin deposit of early Eocene age in the Wilcox Group is mined and beneficiated as a filler and ceramic clay (Fisher et al., 1965). Pence (1954) de- scribed these deposits as nonmarine in origin. They contain 40 to 70% quartz, and the kaolin is a byproduct of a glass-sand operation.

OTHER STATEsKaolin has been mined in the pas! or has been reported present in com- mercial quantities in Arkansas (Tracey, 1944) ,. Illinois (Grim, 1934), Minnesota (Parham. 1970). Mississippi (Conant, 1965), New Mexico (Glassmire, 1957), Vermont (Ogden, 1969). and Virginia (Ries and Sommers, 1920).

REsouRcEsResources of kaolin in the United States of a quality equal to or better than the lower grade clay now mined are at least I billion tons. The one grade of kaolin about which there is concern for long-range supply is the very high grade fine-particle-size white clay suitable as a paper coater and for certain other speciality uses (Buie, 1972). Re- serves of this type of clay probably total 100 to 200 million tons. Potential resources of kaolin, including discolored and very sandy clay and that below more overburden than can be profit- ably stripped at present, are several times the estimated reserves. L: United Kingdom-The United Kingdom is second only to the United States as a producer ?f kaolin or china clay and is the largest ex- a,.

porter of kaolin in the world (Anon.. 19728). China clay is the United Kingdom's chief ex- port, and almost the entire output comes from the SI. Austell area of Cornwall. Historically. the china clays in Cornwall were discovered by William Cookworthy (Barton, 1966) in the mid-1700s to be suitable for making porcelain. In Cornwall, an extensive region of kaolinized granite has been formed by hydrothermal al- teration of feldspar (Bristow, 1969). The gran- ite masses were emplaced in Permian time and are now exposed over large areas of Devon and Cornwall. The china clay deposits typically occur in funnel or troughlike bodies narrowing downward. Hot acidic solutions are thought to have migrated upward, guided by structural weaknesses such as faults and joints, and then to have been trapped under a roof of relatively impermeable rock. The hot solutions attacked the granite, altering the feldspar and mica to kaolinite. Quartz, tourmaline, and mica are the principal impurities. Drilling has shown ka- olinization to exist at depths of more than 800 f t (Bristow, 1969). In most places, the clay can be mined using

high-pressure water jets, but sometimes blasting or ripping is required to loosen the rocks. Se- lective mining is very important because of variability in the various deposits. Much blend- ing is done to produce a uniform product. As the rock face is washed, the slurry containing the kaolin in suspension flows to the lowest point in the pit. The slurry is then pumped into spiral classifiers which remove the coarse ma- terial. After this initial classification, the slurry is pumped to the surface of the pit where hy- drocyclones remove finer sand and mica par- ticles. The slurry is then thickened in large- diameter tanks. A series of refining tanks is used to remove the heavier coarser particles. After primary classification, the slurry is fed to centrifuges to separate the coating kaolin from the filler grade. The kaolin is dewatered by filter presses and is dried. Two new processes have been designed-the tube filter press (Clark, 1968). which utilizes extremely high pressures and produces a relatively dry filter cake that needs little if any additional drying, and a process catalogued as micromineral sepa. ration (British Patent No. 1,222,508), which produces a rather clean pure kaolin.

More than 2.7 million tons of kaolin were produced in England in 1970, of which 2.1 mil- lion tons were exported (Anon., 1972f). The exports are handled through the ports of Par and Fowey. The kaolin is transported to port by rail or truck. Most,ships that transport ka-

.

r .~

olin are in the 400 to 500-ton range, but 1000. ton vessels can be accommodated at Par and 10,000-ton vessels at Fowey.

USSR-Kaolin is mined and processed in several districts in the USSR (Petrov, 1969). Residual, hydrothermal, and sedimentary de- posits are worked. One kaolin deposit in the Transcarpathian region consists of virtually pure dickite (Rusko, 19731, and other deposits in this same district consist of mixtures of ka- olinite, dickite. and halloysite. The Gluhovetski district, southwest of Kiev, approximately mid- way between the cities of Zhitomir and Vinitsa, is one of the major centers of production. The best grades of kaolin are produced from de- posits formed in weathered granite. Production from this district is about 700,000 tpy, and both wet and dry beneficiation methods are used. Another major producing district is in the vicinity of Prosyanovski in the Dnepropetrov- ski region. The deposits in this, area also occur in weathered granite and gneiss. Nearly 1 mil- lion tons of kaolin were produced from this re- gion in 1966. Reserves of kaolin in the Pro- syanovski district are estimated at 160 million tons. Other large kaolin deposits occur in Kazakhstan, where a large kaolin beneficiation plant was reported to be in the advanced stages of planning in 1968. The largest sedimentary kaolin is the Pologa deposit on the Konok River near the Pologa Station. Many other kaolin deposits have been described by Petrov (1969). The Russian kaolin is used in the paper, ce- ramic, rubber, and chemical industries.

Minor Kaolin-Producing Counbies: North America-MExlco-Most of the kaolin in Mexico is in primary deposits originating by hydrothermal alteration of Tertiary rhyolitic rocks (Pasquera. et al., 1969). The deposits are found in almost every state, but the largest commercial deposits are in the central part of the country. All the kaolin in Mexico is dry processed for use in the paper, ceramic, refrac- tories, rubber, chemical, and pharmaceutical industries. Reserves are estimated to be more than 500 million tons. At present, more than 100,000 tpy is mined and processed. Kaolin is imported from the United States for paper- coating applications.

South America-ARGENTINA-The kaolin production in Argentina in 1969 was 80,905 tons (Anon., 1971b). Most of this kaolin was mined in the Blaya Dougnac, Don Carlos, and Maruja districts, Chubut. Districts in Rio Ne- gro and San Juan also had active mines in recent years.

BRAZIL-Kaolin deposits in weathered gran-

.,. . . . .

' .. . : 624 Industrial Minerals and Rocks ~-

i t a , pegmatites, and other crystalline rock; oc- C U I at many localities in Brazil, and rec&tly very large transported deposits have been dir- covered. The deposits in weathered rocks have been mined for domestic use for many yean. The large transported deposits were not de. veloped at the time this report.was prepared, but exploration by American interests and Bra. Z i k n government agencies suggests that prD duction is likely. One region containing sig- nificant deposits of transported kaolin is along the Jari River (Colligan, 1973). a tributary of the Amazon. The deposits along this river arc of Pliocene age (Klammer, 1971). They are ar much as 35 m thick and extend for several ki- lometers. Reserves are considerably more than 50 million tons. Another region in which the kaolin deposits are being evaluated is along the Capim River approximately 200 km- south of BClem (White, 1973).

GUXANA-very large transported kaolin de- ., posits are associated with bauxite in Guyana ' and Surinam (Moses and Mitchell, 1963). These deposits are in sedimentary rocks under- lying the Coastal Plain seaward from a shield area of ancient crystalline rocks, The'regional geology is, therefore, similar to that of the Georgia-South Carolina kaolin belt. Japanex interests are reported to be mining 300 tons of kaolin a month and shipping it to Japan

OTHER COUNTIiIEs-Both residual and trans- ported kaolin deposits occur at several places in Chile, Colombia, and Venezuela (Malkovskf and Vachtl, 1 9 6 9 ~ ) . Hydrothermal deposiu are also present in Chile, as indicated by the association of kaolin with alunite. Small ton- nages of kaolin are also produced in Peru. Paraguay, and Ecuador (Ampian, 1973).

. Europe-The kaolin operations in contine*

tal Europe are mostly small scale because Of the scarcity of high-grade deposits. Most Of the kaolin produced is still used by the ceramia industry and as filler for paper, and only minor quantities are sold for other applications. Germany produces nearly 500,000 tpy k a o h the main production being from Bavaria. kaolin deposits in Brittany in France are being worked to a much greater extent, and Produc- tion from this area will increase substantially. Czechoslovakia. where the production is COLT trolled by the state, is becoming an impoflmt producer, and exports kaolin to other EuroFm countries.

AUSTRIA-Economically important kaolin deposits of'primary origin occur on the BG- hemian Massif, a deeply eroded complex Of

(Ampian, 1973). .>:

granitic and met; Wieden, 1969). the ceramic indur and rubber indust 000 tons were mi 100.000 tons of I

beneficiation tech1 BULGARIA-Sed

probable Pliocenr Bulgaria (Karana vidual deposits ar associated with sa karst area undei limestones. The n' sands is about 18 an iron content 01 used locally in the

CZECHOSLOVAKI principal produce rope. The major c Karlovy-Vary, Plz in west Bohemia ( is primary, is of I the production of and refractories. ? has been mined, a duction will proba tons. Reserves arc 1 billion tons (Ku state controlled, a low price. The I other Eastern Eur last two years a s shipped into Weste Germany (Anon.,

DENMARK-A S:

o h is mined on I marily for the Dal penhagen (Almebc the output goes in alumina refractor! Products. The qua enough to be U S ~ C for paper.

EAST GERMANV- ary kaolin deposit many (Storr, et al.. from an area norti Colditz. The iron mercial deposits rai as high as 2%. M. ceramic purposes, I rubber filler are in mated to be consic lion tons.

-FRANCE-Many kaolin from distric

]line rocks DE.

and recentiy lave been di,. -ed rocks have

many yeao. were not dc. was preparcd. :rests and Bra. :ests that pro. :ontaining "ip. kaolin is along

a tributary <,! s this river arc ). They arc a, for several k8.

ably more than n in which ~ h c 1d-k along thc 0 km south 0:

'rted kaolin dc. tile in .Guyana :itchell. 1963 I . ry rocks undcr. 1 from a shield 3. The repiom! to that oi th: belt. Japanrrc

ing 300 tons c1 g it to Japan

.idua! and tran\- t several placc, ela (MalkovsLi iermal depouir ndicated by thc lite. Small ton- duced in Peru. an, 1973). ins in continen. c d e because d ,its. Most of thc ,y the ceramics and only minor

plications. W e t ,000 tpy kaoiin. m Bavaria. Thc irance are k i n $ st, and produc. s e substantiall!. ,duction is con. 2g an impofinn' other European

,portant Lacjl1!1 cur on the led comple\

. .

granitic and metamorphic rocks (Holzer and the Massif Central in central France. The de- Wieden, 1969). Most of this kaolin is used in posits in Brittany are of approximatelythe same the ceramic industry and as filler in the paper age as those in Devon and Cornwall in England and rubber industry. In 1966, more than 450,- (Anon.. 1972f). In Brittany, the deposits are 000 tons were mined in Austria, but less than all primary in origin: and the deposits around 100,000 tons of this was processed using wet the Massif Central are both primary and sec- beneficiation techniques. ondary (Damiani and Trautmann, 1969).

BULGARIA-Sedimentary kaolin deposits of About 80% of the French production is from probable,,Pliocene age occur in northwestern Brittany and is near the coast. Production is Bulgaria (Karanov, et al., 1969). The' indi- more than 250,000 tpy. Most kaolin is used vidual deposits are small because the kaolin is by the ceramic industry, but its use as a filler associated with sand which fills sinkholes in a for paper, paint, and rubber is increasing be-

. karst area underlain by Lower Cretaceous cause of improved processing techniques now limestones. The average kaolin content in these being implemented. France imports about sands is about 18 to 25%. The best kaolin has 250,000 tpy, mainly from England and the

'an iron content of 0.6 to 0.8%. The kaolin is United States to meet its requirements for used locally in the ceramic and paper industries. kaolin.

.: CzEcHosLovAKIA-Czechoslovakia is the GREECE-Low-grade deposits of kaolin suit-

SPm-+-Spain has the fourth largest produc-

total was 285.000 tons (Anon., 1972f). By 1976, according to the National Mining Plan,

ANcE-Many small companies produce the production will be more than 500.000 tons. Both primary and secondary deposits are mined

filler are increasing. Reserves are esti- tion of kaolin in Western Europe; in 1970, the . '

to be considerably more than 1 0 0 mil-

from districts in Brittany and around ~ -.

626 .-

Industrial Minerals and Rocks

in Spain (Martin Vivaldi, 1969). The deposits are widely scattered, but the commercially im- portant production is concentrated in the north- west near Galicia-Asturias and in the east near Cuenca-Teruel-Valencia. The primary deposits of Galicia were formed by the hydrothermal alteration of mylonitized granite; reserves ex- ceed 300 million tons. The secondary deposits in eastern Spain are Cretaceous in age and are principally kaolinitic sands ranging from 10 to 20 m in thickness. Reserves are estimated to be more than I billion tons. Most of the produc- tion is used by the ceramic industry, primarily in refractories, but as beneficiation techniques improve, more will be consumed in the paper, paint, rubber, and other industries that need tiller clays.

WEST GERMANY-The largest kaolin mining district is in the townships of Hirschau and Schnaittenbach in Bavaria (Anon., 1972f). The deposits are sedimentary in origin, derived from decomposed granite in the Niab hasin moun- tains, and are Triassic in age. These deposits consist of a mixture of quartz, feldspar, and kaolin and are ahout 40 m thick. The material is wet processed to recover about IO to 20% kaolin, and the quartz and feldspar are also salable products. Because of the high content of quartz and feldspar, sophisticated hydro- cyclone-processing stages are used to make very precise particle separations (Anon., 1972f). Other areas in West Germany where kaolin is worked are Oberneisen near Frankfurt, Hesse, and Westphalia (Lippert et al., 1969).

OTHER CouNTRlEs-Srnall tonnages of ka- olin are produced in Romania, Sweden, Portu- gal, Yugoslavia, and Belgium (Ampian, 1973; Malkovskg and Vachtl, 1969h).

Africa-REPusnc OF SOUTH ApnrcA-The kaolin deposits of South Africa have been de- rived from the weathering of granite, shale, and tillite (Coetzee, 1969). Kaolin is mined near Capetown. Grahamstown, and Durban. With the exception of the large deposit of altered till- ite near Grahamstown (Murray and Smith, 1973), deposits are small but of good color and quality. The Grahamstown deposit is very large, with reserves in excess of 50 million tons. but the quality ranges from excellent to very poor and it changes in very short intervals both horizontally and vertically. Approximately 50,000 tons are used locally in South Africa, the ceramic industry taking more than 50% of the production. Other uses include insecticides, rubber, paint, plastics. and pharmaceuticals. The large deposit at Grahamstown could be potentially valuable in the future as advanced

beneficiation techniques become available and water supply to the area is improved. A severe water-supply problem for wet beneficiation of

SWAZILAND-Kaolin deposits of economic importance are found in the Malilangatsha Mountains of the Manzini district (Hunter and Urie, 1969). Kaolinized dikes ranging.in width from 3 to I O m, 75 m in depth, and as much as 620 m in length have been studied. The kaolin ranges from white to pale red, depending on the iron content. The entire production of some few thousand tons is exported to South Africa. . ,

OTHER COuNTRIES~ther African countries having minor kaolin production include An- gola, Arab Republic of Egypt, Ethiopia, Kenya. Nigeria, Tanzania, Malagasy, Mozambique, and Morocco (Ampian, 1973; Malkovskq and Vachtl. 1 9 6 9 ~ ) . The deposits in the Pugu Hills distr!ct %near Dar es Salaam, Tanzania. arc. among those having economic potential. The ',<

kaolin is in upper Tertiary sandstone which is 30% white clay (Harris, 1969). Attractive features of these deposits include a location only 50 km from deep water and a possible glass sand coproduct. However, an attempt in the early 1950s to develop and export this kaolin failed.

Asia-SRI LANKA-The best known kaolin deposit on Sri Lanka is the Boralesgamuwa field, south of Colombo. The kaolin is probably Pliocene or Pleistocene in age, is sedimentav. and occurs in layers and pockets 4 to 19 f t thick (Pattiaratchi, 1969). The percentage of kaolin ranges from 20 to 85, and the major imPUriV is quartz. The kaolin is used for ceramic% paper, rubber, paint, and as an insecticide car- rier. The production is small, about 3000 tPY. and the estimated reserves are about 8 million tons.

INDIA-Kaolin and related clay materials are mined in many locations in India (Arop.Ya,* wamy, 1968). The major producing area 1s !" the vicinity of Chaibasa. The deposit mined I* this district occurs in weathered granite. High- quality kaolin is also produced in the ViclnltY of Kundra, Chattanur, and Quilon, Kerala. The kaolin in this region occurs in altered felds- pathic granite, and the altered zones are as much as 10 m thick.

INooNEsiA-Large residual kaolin depositr altered from granite are known to occur on the islands of Belitling and Banka (private corn. munication). Although the deposits are large. little is known about the quality of the kaolin, There are small wet-processing operationr

kaolin exists throughout South Africa. . .

. .

which produce c industry in lndor

IRAN-The h r j in the central pan (Khadem, 1969). deep weathering i

limestone sequenl: fine ceramic and serves are about 1 :

JAPAN-Large I deposits occur in Shimazaki, 1969) throughout the is1 were formed by h! canic and granitic weathering of grai rock. The second: lower Pliocene ag, 20 m in thickness duced in Japan ( 4 in many deposits tons. The major fine whiteware, p paper fillers. Min difficult each year values and the diR property to sustai operation of a wet

KOREA-Primar: cur in Korea (Hei dry and wet benefi process the kaolin paper, and rubber 000 tons are mine markets; over half Japan for use as g posits. consisting o halloysite: are in th southernmost Kore:

MALAY Sih-Resit granite is being m make paper-filler 'c Kuala Lumpur. T present production

PEOPLES REPUB, only was used first i

in recent trade jou being mined on a for export. Histori, Tae-Chen district i i

were the principal making fine cerami deposits are assoc! Silurian phyllite. T lo white, and it is somably. this distri, this was not veri&

,,, >..,:.- . . ... . . - .. . . . . . . .. . ~ . , _. .

e available and roved. A S C ~ ~ ~ ~ beneficiation ol Africa.

Lfrican countrlG on include hn. %thiopia. lozambiquc.

n the Pug,! iw; Tanzania. A,r potential. 'I k

Idstone which ,, 69). A I l r a c l t ~ ~ :Jude a I O C ~ I , ~ ~ and a p i w h i r

:I, an attempt and export ~h::

it known k a r . i ~ Boralessarnim I

aolin is prohahi) , is sedirnentAr? :s 4 to 19 It I hi<i :entage of Lsul;~. ; major impu:c\ :d for ccinrni.r. 1 insecticidc E ~ I .

about 3000 IT. about 8 ni i l lnm

lay materials J ~ C

India ( A r o p . . ducing areca i* ria

deposit rnincl! I::

d granite. HiFh d in the \,icinilL Ion, Keraln. 'lk in altered fclJ$ Ed zones :irc

. r n O V S k ? a,)i!

kaolin dep-cl:' 7 to occur on Ih- .a (privatc cmr- eposits a re I W C .

ify of the kai.11" ising opcratirn,

which produce china clay for the ceramic industry in Indonesia.

IRAN-The largest kaolin deposit in Iran is in the central part of the country near Simiron (Uadem, 1969). This deposit is the result of deep weathering at a diastem in a Cretaceous limestone .sequence. The material is used for fine ceramic and refractory purposes. The re- serve~ are about 15 million tons. . JAPAN-Large primary and secondary kaolin deposits occur in Japan (Fuji, Okamo, and Shimazaki, 1969). The deposits are scattered throughout the islands. The primary deposits were formed by hydrothermal alteration of vol- canic and granitic complexes and from in-situ weathering of granite, pegmatite, and volcanic rock. The secondary deposits are lacustrine, of lower Pliocene age, and range from 20 cm to

'20 m in thickness. About 200,000 tpy is pro- duced in Japan (Anon., 1972f). The reserves

'in many deposits range from 5 to 20 million :tons. The major uses of the kaolin are in :fine whiteware, pottery, refractories, and as 'paper fillers. Mining in Japan becomes more diflicult each year because of increasing land

.values and the difficulty in purchasing enough property IO sustain reserves required for the operation of a wet-beneficiation plant.

KOREA-Primary and secondary kaolins oc- cur in Korea (Heikes and Kim, 1965). Both dry and wet beneficiation methods are used to process the kaolin for the ceramic, refractory, :paper, and rubber industries. More than loo_- OM) tons are mined for domestic and export .markets; over half of this is shipped crude.to :Japan for use as paper filler. The largest del posits, consisting of mixtures of kaolinite and .halloysite, are in the Hadong-Sanchong afea of wuthernmost Korea.

MALAYSIA-Residual kaolin altered from ; p i l e is being mined and wet processed to make paper-filler 'clay (Anon.. 1970f) east of (Kuala Lurnpur. The reserves are large, but 'present production is only about 5000 tpy. 5 PEOPLES REPUBLIC OF CHINA-Kaolin not 'only was used first in China, but advertisements :in recent trade journals indicate that it is still :being mined on a large scale and is available 'for export. Historically, deposits in the Ching- :Tae€hen district in Fuliang, Kiangsi Province. &ere the principal source of kaolin used in $aking fine ceramic ware (Pai. 1945). These 'iJeposits are associated with Ordovician and Silurian phyllite. The clay is mostly light gray $6 white, and it is 70% pure kaolinite. Pre- rumably. this district is still in production, but @ was not verified. Other kaolin-producing

%

:-

5 . -

.-

regions in China include Singtze. Loping, Yu- kan, and other districts in Kaingsi Province, and Tzuhsien, Kaiping, Fengyn, and Chingh- sing, Hopeh Province. Kaolin in deeply weath- ered granite occurs at several localities in Kwangtung Province which surrounds Hong Kong. This kaolin formed from granite may he the clay advertised for export because it is much closer to the ocean than most other deposits.

In addition lo the kaolin mentioned in the foregoing paragraph, kaolinitic clays asso- ciated with diasporic and bauxitic clays in Carboniferous, Permian, and Mesozoic coal measures occur' in Szechuan, Honan, Kupeh, and Fukian Provinces and elsewhere. Several of these clays are called kaolins and are used in ceramic products. Residual kaolin formed by the weathering of arkosic sandstone occurs in Szechuan Province, and deposits formed from weathered feldspar in granite and peg- matite occur at several places in China.

PHILIPPINES-Philippine kaolin deposits are primary and are generally small and scattered. Most are hydrothermal in origin, although one deposit called Bukidnon is believed to have formed from in-situ weathering of a dacite (Cornsti, 1969). The major deposits are on Luzon and Mindanao. The bulk of the kaolin is used in refractories, tiles, and sanitary wares. Very little is used in the paper and rubber in- dustry. The reserves are limited and transporta- tion is costly; these factors and the variable quality of the kaolin make the mining opera- tions very marginal.

Turkey-Both primary and secondary kaolin deposits are mined in Turkey, primarily for the Turkish ceramic industry. Approximately 100,- 000 tons of kaolin are used annually in Turkey by the ceramic industry (Jeyhdn, 1969). Re- serves, estimated at 2.5 million tons, are mainly in the western half of the country.

OTHER COUNTRIES-The production of ka- olin has been rcported in recent years (Ampian, 1973) in Pakistan, Taiwan, Thailand, and South Vietnam.

Ocearlia-AUSTRALIA-Most of the kaolin deposits in Australia are primary and have been formed as a result of deep weathering of both silicic and mafic rocks (Gaskin, 1969). Sec- ondary deposits in Western Australia are asso- ciated with the coal measures of Cretaceous age. Some of the Australian kaolin is very . , white and can be used readily as filler and for ceramic purposes (Anon., 1970g), but the vis. cosily of almost all the kaolin is very high,

- -. -

..

628

e-. ' . I 31 r <- ' _- . ~.. Industrial Minerals and Rocks . .

which prohibits its use for paper coating. The bulk of the kaolin produced is used for refrac- tories: the rest is consumed by the ceramic, paper, paint, plastics, and rubber industries. Although no precise estimates of reserves have been made, the total amount of kaolin in Aus- tralia is known to be very large. At present. more than 100,000 tons is processed in Aus- tralia primarily for local consumption. although some is being exported to Japan as paper filler. Most of the deposits mined are within 200 km of the major cities of Melbourne, Sydney, Adelaide, and Perth. Extensive exploration for kaolin is being carried out in Australia by sev- eral major companies, primarily because of the lucrative Japanese export market.

NEW ZEALAN-The only kaolin being pro- duced in New Zealand at present is in the Northland some 120 km north of Auckland (Bowen, 1969). The deposits are hydrother- mal and are mixtures of kgolinite and. halloy- site. Reserves are estimated to be approxi- mately 20 million tons. The kaolin is wet beneficiated for use as a ceramic whiteware component and as filler for paper and paint. The kaolin is very bright and white but has a high viscosity and is somewhat abrasive, which prohibits its use in paper coating. At present, the entire output of some 5000 tpy is utilized in New Zealand.

Exploration, Evaluation

Exploration in the United States: The princi- pal productive deposits of kaolin were found in the Carolinas and Georgia in the late 19th and early 20th centuries. Most discoveries were in outcrops in stream beds and road cuh. Today, exploration is carried out in geologically favor- able areas, taking into account topography and elevation. Geologic and topographic maps, if available, and aerial photographs are used to lay out exploration drill-hole patterns. Most exploration holes are drilled to depths of as much as 200 f t and on 400- to 800-ft centers. Many deposits were missed in the past because. only random spot drilling instead of pattern drilling was used. Also. because drilling was limited to 50 or 60 ft. many goad deposits at greater depths were not discovered. Auger or fishtail drills are used to the top of the kaolin bed, and then a special core barrel is used to core the kaolin. Cores are difficult to mover , and special care by expert drillers is necessary to get good core recovery. In many areas, two

: x ,. or three kaolin beds separated by sand are pen& : trated where drilling is as deep as 200 ft. z :..\

Many geophysical methods of exploration for 6 kaolin have been attempted, but to date none has been successful (Gross, 1960). Geochemi- cal techniques also have been unsuccessful. The only positive method to locate and delineate kaolin deposits to date is by pattern drilling

Evaluation of Deposits: After coring th kaolin and recording the thickness of the vari- ous strata above the kaolin and the thickness of the kaolin bed, a large-scale map is prepami On this map, the drill holes are located and thc thickness of the over-burden and the kaolin arc recorded. The cores are sent to the crude evaluation laboratory where the kaolin is pn- pared and tested.

The cores are cleaned and divided into sec- tions 2 f t or less in length for testing. The m- son for splitting the cores into short sections u t e b e able to spot any lens or section that mby% be off-color, have high grit or high viscosity, or not meet specifications in some way. The 2-A sections are dried and pulverized. The pub verized material is then evaluated using tk following tests for paper-type kaolin:

1 ) Percent grit or screen residue ~ _ - 2) Particle-size distribution 3) LOW shear viscosity 4) High shear viscosity 5 ) Brightness

Grit percentage is determined as explained i!J the section on end uses and specifications and is an important crude evaluation test. A , g d rule of thumb is that as much as 5% grit C a n be handled easily using air-flotation techniqua Much higher percentages of grit can be dled using wet beneficiation methods, but * higher the grit percentage the, lower the * covery of kaolin and the higher the cost. Nor- mally in the United,States, a maximum of l o to 15% grit is set for the upper limit of @ percentage, but if the kaolin is of unusuallY high quality, a higher grit percentage Can tolerated.

Particle-size distribution is important b s a y from this test the percent recovery Of coating and filler clays is determined. For many Yern an important delineatidn point has been percent of particles less than 2 micrometen in size (Lyons, 1966). This percentage Can vaq from as low as 50% to as high as 90% In * Georgia deposits. This is an important test k-

_ - ..

. .

~ . _-. . ,. .. . ~.

~ . :._....".- .I .~>. ._ r 6) Leachability . ' ~ .. . s z . * = .

cause brightnes: properties are cI a predeterminec plied to the bene and coating req uniform process necessary to blt posits to regular terial being fed the testing, one are prepared. N tain 80% of the ters in size. If s a coating clay fr particles less th; prepared.

Both low shea] are run on the di coating fraction I The upper limit < be tolerated is 8( shear of 300 rpn The low shear vi: ropy, and high st tion of dilatancy {

Brightness is m, clay and on .the No. 2 coating cla) ten) a minimum quired, and for N than 2 micromete quired. Brightness lowing procedure?

Leachability is fractions to deter, that can be attail and oxidizing leac minations are ver) lishes the level of kaolin can be utilii to meet brightness

For air-float cla are determined. F, ness, green and dr) determined. Chen alumina are commc

a refractory pro. be important are t Centage of particle In size, percentage titularly smenite, area, and the quant. sary to attain the lo

After all the tesi ated and the over! thicknesses of the mined, a decision i

by sand are pent. :3 as 200 f t

After coring t;f, kness of the Y ~ , , .

.d the thicknell o! map is prepared :e located and t& Ind the kaolin arc :nt to the crud< the kaolin is prc.

divided into %. testing. The IC*.

0 short section, t,

' section that mi) high viscosity,

ne way. The ?.!: erized. The ptii. rluated using thc

:sidue

kaolin:

I

ed as explaincd tn

specification\ an2 :ion test. A g o d h as 5% grit can tation techniqucr grit can be han. methods. but Ihc he lower thc rc. er the cost. Nor- maximum of I O

>per limit of gri: 1 is of unusuall? ercentage can Ir

mportant becaux :overy of coatin6

For many ycan nt has been the 2 micrometers In centage can mr?' :h as 90% in thc mportant. test h.

cause brightness, viscosity. and other physical properties are closely related to fineness. Also, a predetermined fineness range must be sup- plied io the beneficiation plant to meet the filler

.I and coaling requirements and lo provide for uniform process procedures. It is, therefore. necessary to blend kaolins from various de-

action containing 92% of the n 2 micrometers in siFe is.

Both low shear and high shear viscosity tests degritted crude clay and on the

No. 2 coating clay (80% finer than 2 microme- ten) a minimum brightness of 85.5% is re-

. quired, and for No. 1 coating clay (92% finer

rburden thicknesses and the e deposit have been deter.

. .

Clays is of a quality suitable for any of the present uses for kaolin or a potential aluminum re- source, or whether the property should be dropped. The economic limits of the ratio of overburden to kaolin that can be mined eco- nomically range between 6 and 8 to I , depend- ing on the type of overburden, and the reclama- tion requirements imposed by federal and/or state law.

If the decision is made io keep the deposit for future mining, then additional drilling is done on 200- or 100-ft centers. From this drill- ing information, additional maps and cross sec- tions are prepared, from which a stripping and mining plan is devised.

The classification of a deposit as potential aluminum clay is of relatively recent practice as a result of the interest in using kaolin as a raw material lo produce aluminum. The United States is dependent on foreign sources of baux- ite to supply approximately 90% of its alumi- num requirements. The purchase of bauxite represents a significant outlay of dollars which contributes to our balance of payment deficits. Kaolin clays in Georgia and South Carolina contain 35 to 39% AI?O, and represent a very sizable resource from which aluminum could be recovered if the economics become favorable. A report by the National Materials Advisory Board (Anon., 1970i) reviewed the various processes for extracting alumina from non- bauxite ores. An article (Anon., 1973b) also described a process to make aluminum using high-alumina clay which is chlorinated and reacted with manganese to form aluminum. Coal is used as the fuel.

Preparation for Markets

Mining and Beneficiation: The mining of kaolin is a highly sophisticated mechanized operation (Murray, 1963b). After extensive testing to insure that the deposit can be bene- ficiated to meet the necessary quality standards of the various process industries, mining plans are prepared which include clearing of timber, removing the overburden by either motorized scrapers or large draglines, establishing a land- reclamation schedule and program that must be approved by officials in some states, such as Georgia, and establishing approved environ- mental controls on water drainage and dust emanation. After the overburden is removed and the top of the kaolin deposit is exposed, additional drilling is done in order to provide detailed information of quality variations within the deposit so that a predetermined mining program can be followed that will meet the

.. . . - . . Industrial Minerals a n d Rocks ~

requirements needed by the beneficiation plant. Detailed maps showing the elevations of the top of the kaolin, thickness of the deposit, all quality determinations, and lateral extent are prepared which are used to control the mining operation properly.

The principal beneficiation steps are shown in Fig. 11. After the kaolin is exposed and tested. the kaolin is mined by shovels, draglines, motorized scrapers, or front-end loaders. The kaolin is either loaded in trucks or dropped into a blunger which disperses it in water with the aid of a dispersant chemical to form a clay- water slip or slurry. This slurry is pumped from the blunger to a degritting station, where, by the use of settling boxes, screens, and/or hydro- cyclones, the coarse foreign particles called grit are removed. Grit is defined as that material coarser than about 44 micrometers. After de- gritting, the kaolin slurry is collected in large storage tanks and then pumped through pipe- lines to the beneficiation p l a n t

Two basically different processes are used to produce a salable kaolin product-a dry proc- ess and a wet process. The dry process is sim- ple and yields a lower cost and lower quality product than the wet process. In the dry proc- ess, the properties of the finished kaolin reflect generally the properties originally found in the crude kaolin. Therefore. deposits containing the desired qualities of brightness, low grit con- tent, and particle-size distribution must be Io- cated by drilling and testing. In the dry process. the kaolin is crushed to approximately egg size, dried in rotary dryers, pulverized, and air- floated. The air-floating process removes most of the grit.

The wet process (Fig. 11) has been highly developed in recent years to produce kaolin products of uniform and predetermined physi- cal and chemical properties. Crude kaolin of variable quality can he wet processed to pro- duce a uniform high-quality product.

The kaolin slurry is pumped from the mines to the plant, where it i s stored in large tanks. Kaolins of various qualities are blended at the mine tanks or in the terminal tanks at the plant to provide a feed for the beneficiation plant that will produce products to meet specifications. The first step in the wet process is to fractionate the kaolin slurry into coarse and fine fractions by using continuous centrifuges, hydrocyclones. or hydroseparators (Fig. I 1 1, After fractiona- tion. the kaolin is leached to remove ferrugi- nous coloring compounds. In this step the ka- olin is acidified with sulfuric acid to a pH of about 3.0 to dissolve the iron, A strong reduc-

. . ing agent such as a hydrosulfite is then added. and the iron reacts and forms a soluble sulfate, which is removed during the dewatering step. The dewatering of the flocculated kaolin slip is accomplished by using high-speed centrifuges, rotary vacuum filters, or filter presses. Some- times the flocculated slip is thickened by using thickeners or centrifuges before filtration. After filtration, the kaolin filter cake can be extruded to noodle form and dried in apron dryen or rotary dryers or it can be redispersed to the fluid state and spray dried, drum dried, or shipped in slurry form as 70% solids in tank cars.

The foregoing paragraph is a simplified de. scription of the wet process. Other processes are used to produce brighter and whiter kaolins and to reduce viscosity. Flotation (Greene and Duke, 1962), selective flocculation (Bundy and Berberich. 1969). and magnetic separation (lannicelli, et al., 1969) are used to remove iron'inki 'titanium impurities to produce kaolin' .. in the range of 90% hrightness.._This kaolin has a blue-white shade.

The most recent. development for improving brightness and whiteness is a high-intensity magnetic separator which removes substantial quantities of iron and titanium mineral im. purities. The intensity of these newly developed units ranges from 18 to 22 kilogauss. The main feature of the separator system (Fig. 12) is a canister filled with a special type of fine steel wool which provides a uniform magnetic field through which the kaolin slurry is pumped 2nd the magnetic particles retained in the'matris. Periodically, the magnet is deenergized, and a high volume of water, under pressure is back Rushed through the matrix to flush out the Im- purities (Oder and Price, 1973).

Delaminated kaolin is produced by splittin% apart the larger books or stacks of k a o h (Fig. 13); this yields a product in which the individual plates tend to be wider. thinner. and whiter. The processes used for'delaminatlo* include wet attrition grinding (Gunn and Mor- ris. 1965) and extrusion (Lyons, 1959). De- laminated kaolin has special application in 1iP.h.'- weight paper coatings, in paint films, and I n special rubber applications.

Calcination is another widely used process Io produce special products from kaolin. WheT kaolin is heated to approximately 1050°C. it Is converted to mullite, silica-alumina spinel. and cristobalite. The product is whiter, brighter. better hiding properties when used in thin f i l m applications, and is more abrasive.

Other special processes are used to modify

'.

-. . . . ~

.

PROSPECTING &NO MINE PLANNING

LEACHING (To whiten and brighten kaolin)

.

DISPERSING c CHEMICAL ~2

FIG. 11--1/1

then added, .hie sulfate, itering step. -aolin slip ii centrifuge,,

m s . somc. e d by using ation. Aftrr be extruded

'n dryers or x e d to n dried. )lids in tank

'mplified de. :er procesrer hiter kaolin, (Greene and (Xndy and : separation 1 to remnvc Jduce kaolin This kaolin

)r improvini ligh-intensi!) s substant;;,l mineral im.

,ly develowi! is. The main 'tg. I ? ) is 2 of fine SIPC!

iagnetic ficid pumped and the matrt\

.gized. and a sure is bark 1 out the in,.

I by spliltin~ .s of ka01i:i :n which thc thinner. anJ

de1aminalio.n nn and %lor. 1959). Dc.

ition in light. ilms, and / n

ed proceSS to lolin. \ V h m IOSO'C. i t i\ a spinel. and brighter. h:w

I in thin film

d to modif?

_.

Industrial Minerals and Rocks

Sl iEL nml YAIR X

CAN SIER WALL

TOP VIEW

Y f f i N i T STEEL, SLURRY OUT

7- MATRIX-

YAGNLT COIL- CANISTER-

SLURRY IN I] * SIDE VIEW

SECTION THRU MAGNET

FIG. 12-Diagrammatic illustrotion of mag- netic separator used in removing iron and very

fine-grained titanium minerals from kaolin.

the surface of the kaolin chemically to improve its function in many systems, such as ink, rub- ber, paint, and plastics. These surface-modified kaolins can he hydrophilic, hydrophobic, or organophilic.

Transportation: The kaolin products are shipped from the heneficiation plants in bulk, in slurry form at 70% solids, and in multiwall paper bags. Kaolin is supplied commercially in pulverized form, in lump, generally in the shape of small extruded noodles, in spray-dried bead form, in small pellets, or in flake form. The weight per cubic foot of the kaolin will vary

Pbter Kaolin sbck

FIG. 13-Diagrammatic illustration of the splitting of kaolinite booklets or stacks into

thin plates by the delmination process.

widely depending on whether it is in pulveriied, lump, bead, or in some other form. Lump clay will generally weigh 60 to 65 Ih per cu ft. Spray-dried clay in bead form will weigh 40 to 50 Ib per cu ft. Depending on the fineness of pulverization and moisture content, pulverized kaolin will range from ahout 35 Ib per cu ft for air-floated kaolin to as low as 20 Ib per cu ft for some very fine particle Size finely pulverized kaolin.

Kaolin is shipped in hulk form in boxcars, in covered hopper cars, and in slurry form in tank cars or in tank trucks. Kaolin is also shipped in 50-lh multiwall bags in boxcars or in trucks when the customer cannot handle the material in bulk. Export shipments are made in bulk ore-type carriers in 2,000- to 15,000-ton lots, in either lump or spraydried form. Some export tonnage is also shipped in special paper

,bags of 25- to 50-kilo capacity. Markets and Consumption: The variou!

markets to which kaolin is supplied were dis- .~ cussed in the section on end uses. In 1980, 7,878,993 tons of kaolin were produced and sold in the United States (Table I ) . Fig. 7 shows the tons of kaolin sold for use as paper filling and coating, rubber, ceramics, refracto- ries, and other uses for the years 1929-1979. Since 1930, the market for kaolin has increased tenfold. In the 1930s, practically all the kaolin sold to the paper industry was used as filler, whereas today the proportion of filler clay to coating clay sold to the paper industry is a p proximately 1 to 2. Coating clay has a much higher value per ton than filler clay, and this increase in the use of coating clay has had more effect on the kaolin industry than any other single factor over the past 40 years. In 1980. the total value.of kaolin sold was reported at $527,098,609 (Ampian and Polk, 1981).

Exports of kaolin to Europe, Japan, and South America have increased significantly from 1965 to the present largely because Of the increasing use of coating clay by the paper industry. In 1980, 1.,392,000 tons of kaolin ,having a value of $133.7 million, was ex- ported (Ampian and Polk, 1981). The largesf export tonnages of kaolin are shipped from Savannah, GA, and Port Royal, SC.

Future Considerations and Trends: Cooper (1970) has estimated that the demand for ka- olin from the United States in the year 2000 will be five to six times greater than the amount now being sold. He has estimated a high of 23,680,000 tons and a low of 16,710,000 ton: He has assumed a technological and ecOnOmlC breakthrough that will allow kaolin to be used

for the producti, If this projectio future of the kai and dynamic.

Competitive p calcium carbonai silicates, alumina Ground calcium fer color, and ha: however, has be gives befter hidir ground calcium c tages with respec in acid finishes, ( nate panicles ar, gloss, (3) it giver high solids, and cipitated calcium paper to give hig receptivity.

Talc competes caulking compouh In paints, talc gi\ ting in interior pai

Precipitated si1 reinforcement to I strength, modulus abrasion. These paper to improve TiO, used in pap one-third to one-h: the precipitated si1 only in conjunct specific requireme

~ Alumina hydra1 turing to give higl EOl. It is seldor, with kaolin. Alun times more expens

The drive to prc paper has led to th ments which are I

and spherical (A Shand, 1973). Tt rior properties suc proved printahilit!, much more expen: ments will be blen b i n improved pro! tions but will not. pigment.

Ball Clay

History and Use. Of the material no. in the United Star Paris, TN in 186(

t is in pulverized. arm. Lump clay 55 Ib per cu f t . will weigh 40 t o

n the fineness of ntent, pulverized 5 Ib per cu r t for i 20 Ib per cu 1, .. finely pulverized

form in boxcan, n slurry form i n

Kaolin is aIm 8s in boxcars annot handle the m t S are made in 0- to 15,000-la" :ied form. somr in special papcr

I: The variou, pplied were di,. uses. In 1 Y N r r .

e produccd m d ' ible 1 ) . Fig. 7 for use as papcr .amics, refratlo. 3ars 1929-1970. lin has incrmsd 'ly all the kaoliri s used as fil lcr. of filler clay to industry is ap

lay has a much r clay, and !hi\ iy has had mwc than any othcr fears. In 1 9 S O . #as reported at k, 1981). E, Japan, and :d significantly ely because of iy by the paper tons of lnolin illion, was ). The largo: shipped fron: sc.

rends: Coopt:' lemand for k3. the year 2000 Ian the amounl lted a high @f

;,710,000 tons. and emnomic

ilin to he u r d

-.

. . . .. .. . . . . . - . . . . . .. . - __ - - ?I . . ... , .. -7.; . , .- r ..

Clays 633

for the production of alumina and aluminum. If this projection is even partly correct, the future of the kaolin industry is indeed exciting and dynamic.

Competitive products for kaolin are ground calcium carbonate, talc. precipitated silica and silicates, alumina hydrate, and plastic pigments. Ground calcium carbonate is cheaper, has bet- ter color. and has lower oil absorption. Kaolin, howeve;, has better Row characteristics and gives better hiding or opacity. In paper uses, p u n d calcium carbonate has several disadvan- tages with respect to kaolin: ( I ) it is reactive in acid finishes, (2) the ground calcium carbo- nate particles are too large to produce high gloss, ( 3 ) it gives poorer Row characteristics at high solids, and (4) it is more abrasive. Pre- cipitated calcium carbonate is used in coating paper to give higher brightness and better ink receptivity. r Talc cornwtes with kaolin mostlv in paint. 'caulking compounds, and drywall c&np&nds: 'In paints, talc gives better brightness and flat- :ling in interior paints. ;. Precipitated silica and silicates give better .reinforcement to rubber, produce higher tensile strength, modulus of elasticity, and resistance to abrasion. These materials are also added in paper lo improve brightness and to extend the Ti02 used in paper. However, kaolin is only one-third IO one-half as expensive; consequently the precipitated silicas and silicates will be used only in .conjunction with kaolin to achieve .specific requirements.

Alumina hydrate is used in paper manufac- turing-to give higher brightness and to extend -TiO,. I t is seldom used alone but is blended .with kaolin. Alumina hydrate is two or three

: . The drive to produce very lightweight coated paper has led to the development of plastic pig. rments which are uniform in size. lightweight, :and spherical (Anon., undated; Heiser and $and, 1973). The pigments give some supe- por properties such as gloss, opacity, and im- :proved printability to coated paper hut are :much more expensive than kaolin. These pig- 'ments will he blended with kaolin to give cer- tain improved properties for particular applica- tions but will not replace kaolin as a coating

times more expensive than kaolin. . .

. .

i . $merit. :Ball Clay p

History and Uses: Probably the first deposits ;of the material now known as ball clay mined $ the United States were those worked near Paris, TN in 1860 for use in a local pottery

(Hosterman, 1973). The first clay shipped to out-of-state consumers was that produced in west Tennessee in 1894 by a Mr. I. Mandle. Later, the industry expanded into Kentucky, and the ball clay districts in the western parts of these two states competed with districts in the United, Kingdom (Anon., 19694) for the world leadership in production. In 1981, more than 916 thousand tons of ball clay was pro- duced in the United States (Ampian, 1982). More than 80% of this tonnage was produced by companies active in Tennessee and Ken- tucky. The other states producing ball clay are Mississippi, Texas, and California (Fig. 10). Ball clay is also produced intermittently in Maryland.

Ball clay i s used principally in the manufac- ture of vitreous china sanitary ware, electrical porcelain, floor and wall tile, dinnerware, and arlware (Phelps, 1972). It is also used in re- fractory products, ceramic glazes, and porcelain enamel slips.

Geology: Miflerdogy-Kaolinite is the prin- cipal mineral in the ball clay deposits in Ten- nessee and Kentucky, but other clay minerals are present and nonclay minerals vary appre- ciably in abundance. The kaolinite in these de- posits is fine-grained, and much af it is poorly ordered. The main clay minerals other than kaolin are illite, smectite, chlorite, and mixed- layer clay. Quartz is by far the most abundant nonclay mineral; in some deposits it makes up as little as 5% of the clay, but in others, as much as 30% (Olive and Finch, 1969):The other nonclay minerals ordinarily present occur in very minor or trace amounts and include plagioclase, potassium feldspar, and calcite. Or- ganic matter in the form of black leaf imprints and disseminated lignitic and peaty materials are common in most ball clays.

Occurrence and Origin-Ball clay is ex- tremely plastic. Deposits range from very light gray to nearly black. Most deposits are lenticu- lar bodies varying considerably in size and shape. Some are more than 30 ft thick and extend over areas 1000 ft wide and 2500 f t long, but most deposits are smaller. The physi- cal.properties of a typical deposit vary con- siderably, and layers and pockets mined from a given deposit are commonly separated in dif- ferent stockpiles suitable for a particular use.

Most deposits in Tennessee and Kentucky are in beds of Claiborne age (middle Eocene), but a few, including one mined, are in Wilcox beds (lower Eocene) (Olive and Finch, 1969). The deposits mined in Texas near Henry's Chapel, northeastern Cherokee County (Fisher

Indus t r ia l Minerals and Rocks

et al., 1965) are also in Wilcox beds. The ball clay mined in Paoola County, Mississippi (Bicker, 1970). is in a formation of Claiborne age, and the deposits are approximately the same age as younger ones in Tennessee and Kentucky. The deposits mined in Stanislaus County, California, are in beds of Paleocene or Eocene age (Cleveland, 1957). Those mined on a small scale in the Hart district in eastern San Bernardino County, California, are in hy- drothermally altered Tertiary rhyolites (Kelley,

,1966). Most ball clay occurs in transported sedi-

mentary deposits, but one minor producing dis- trict in California contains hydrothermally altered clay. The deposits in the Tennessee, Ken- tucky, and Mississippi districts are in sedimen- .tary formations cropping out along the eastern edge of the Mississippi embayment. According to one theory of origin (Olive and Finch, 1969), they accumulated in an elongate broad valley. The abundance of plant remains and organic matter associated with this clay indicates that the depositional basins probably were swampy.

Distribution of Deposits: (Inired Stares-Any attempt to estimate the resources of ball clay is based on piecemeal information. The reserves, primarily in Tennessee and Kentucky, total probably as much as 100 million tons, and are owned by eight or ten different companies; they are thought adequate to sustain the industry for 100 years (Phelps, 1972). Additional reserves are in the producing districts in Mississippi, Texas, and California. Potential .resources of low-grade ball clay, which probably would re- quire beneficiation for market, occur in the vi- cinities of all of these districts. The prospects are also favorable for the discovery of more deposits of kaolinitic clay having the physical properties'of ball clay in several southern states. Furthermore, if the term ball clay is applied to such deposits as the hydrothermally formed clay at Hart, CA, many areas in the western states are likely to contain large deposits.

Orher Counrries-The principal ball clay de- posits in the United Kingdom occur in the Bovey Basin southeast of Dartmoor in Devon- shire, the vicinity of Petrockstow in north Devonshire, and in the Wareham and Poole regions of Dorsetshire. These ball clays occur in sedimentary rocks of Tertiary age. consisting mainly of lenticular units of sand, clay, and lignite of probable lacustrine origin (Scott, 1929). The clay is very fine grained plastic kaolin ranging in color from off-white to dark brown and gray. The darker colors, as in the

... . ... ball clay in Kentucky and Tennessee, appar- ently are caused by carbonaceous impurities, -: and the clay burns white. The deposits arc believed to have been transported from altered ; granite and other igneous rocks. Watts, Blake, i Bearne, and Co. is the major producer of ~' . ~3 . ... :i . . .Y

Ball clay occurs at several localities in india (Arogyaswamy, 1968). but production is lim- ited, and in recent years India has been an im- porter of ball clay. The best quality ball clay produced is in the Than district of Gujarat. Other deposits are mined in two districts i n .

.. ... .... .- British ball clay. .. ' '

~

. . . Kerala. -.. . .:.:;:;:~:-

Evaluation of Deuosits: The DrosDectinr f - _ . . techniques for ball clay are very similar to those outlined for kaolin. The most commonly . ' used tests are very similar to those used for '

evaluating the ceramic properties of-kaolin and heat-resistant properties of refractory clays. Chemical analysis for soluble sulfate in ball clays.,is commonly required because this ma. . terial 'can be tolerated in only very minor

Preparation for Markets: Ball clay is mined by stripping methods and trucked to plants. Most plant processing involves primarily drying and grinding to a suitable size. A few planu air-float part of their output. Most ball c!ay is packaged in paper bags, but some is shipped in bulk carload lots in both crude and processed form. In recent years, some ball clay has been : shipped in tank cars. This clay is prepared for . shipment by deflocculation ,in water, and it b shipped as 60 to 62% solids (Pbelps, 1972). ; Such slurries are used by plants manufacturing ' ceramics by the slip-casting method. . Future Considerations and Trends: The PI*

duction of ball clay in the United States has grown rather consistently for the last several decades, and continuation of this trend is fore- cast. Nationwide demands are likely to be 2 to 2.3 million tons in the year 2000 (Cooper. 1970). In general, the ball clay industry faces little competition from foreign sources, and exports are appreciably greater than imports. However, the major districts in Tennessee and Kentucky are in the central part of the coun- try and as rail transportation costs increase. a greater proportion of the demands in the POPu- Iotis coastal region may be satisfied by imports.

.

amounts in most ceramic products. .

. - a

. .

'- / .- .t

Halloysite ~ .! . History and Uses: Apparently the first

Ioysite used in the United States was that mined on a small scale near Rising Fawn, GA in the

. . . . . -:. ____ -I . L . . _.,

late 1800s. This sold as a filler < 1909). Deposits and used for ma) hurst and Teague of halloysite. was diana and used fa after World Wa. major source of been the approxi from the Dragor (Fig. IO), by Tt essed into petrol Filtrol Corp. pln Mining to suppl Minor tonnages from this same mi Halloysite occurr Utah has also bee brick, firebrick, ti Sant, 1964). Ha used in portland c 1971). Deposits kaolinite and hall, (Hosterman et al.. lar clay-mineral C I

(Parker, 1946) ai and other product

Geology: Mine lar to kaolinite tt guished without (Brindley, et al.. structures comml micrographs of.de loysite) are ordin eral. The shortco not all metahallc form. 'A. reliable (001) spacing of 10A: as halloysite halloysite, the spa which is essential kaolinite. Halloys fied by the greate grams of samples

Nonclay miner2 loysite vary consi. Some deposits, s i mine, Utah, are e; only minor quan sisting chiefly of bearing. minerals and manganese OX

deposits, silica is curs in the form and poorly crysta. deposits are interr-

. - ... .

'calities in indla oduction is ii(,,. has been an in,. Wality ball cia) yict of two districts in

he prospcctinF very similar t u most common!) those used fi,,

es of kaolin anti

sulfate in ha(: :cause this n,;. I ~ Y very minm lucts. II clay is mined cked to plant, Jriniarily drying . A few pl;,n~, 40st ball cia? i\ ne is shippd i n ; and procchd II clay has her,: is prepared fot

water, and it i\ Phelps, 197:i manufacturin~ hod. ,ends: The pi<,. ited States h.1, he last sevcral s trend is forr. likely to bc >

ZOO0 (Coowr. industry fnccr

I sources. nnJ than import..

Tennessee an<! -t of the coun. s t s increase. ;I 3s in the POP". !ed by import(.

: m t o r y Cl+,

y the first hal. was that m i n d wn. GA in thc

late 1800s. This clay is reported to have been sold as a filler or extender in food (Veatch, 1909). Deposits near Gore, GA were mined and used for making alum about 1912 (Broad- hunt and Teague, 1954). A few hundred tons of halloysite, was mined from deposits in In- diana and used for pottery and alum during and after World War 1 (Callaghan, 1948). The major source of halloysite in this country has been the approximately 1 million tons mined from the Dragon mine, Tintic district, Utah (Fig. l o ) , by The Anaconda Co. It is proc- essed into petroleum-cracking catalyst at the Filtrol Corp. plant in Salt Lake City, Utah.' Mining to supply this plant began in 1949. Minor tonnages of halloysite were produced from this same mine before 1949 for other uses. Halloysite occurring at several other places in Utah has also heen used in making light-colored brick, firebrick, tile, and as a paper filler (Van Sant, 1964). Halloysite in Nevada has been used in portland cement in recent years (Papke, 1971). Deposits in Idaho consisting of mixed kaolinite and halloysite are used in refractories (Hosterman et,al., 1960), and deposits of simi- lar clay-mineral composition in North Carolina (Parker, 1946) are mined for use in ceramics and other products.

Geology: Mineralogy-Halloysite is so simi- lar to kaolinite that the two cannot he distin- guished without careful mineralogical work (Brindley, et al., 1963). Very fine tubular structures commonly observable in electron micrographs of dehydrated halloysite (metahal- loysite) are ordinarily diagnostic of this min- eral. -The shortcoming of this criterion 'is'-thaf not all metahalloysite occurs in ' the tubular

-form. A reliable criterion is that the basal (001) spacing of halloysite is at approximately 1OA; as halloysite converts irreversibly to meta- halloysite, the spacing collapses to about 7.2A, which is essentially the same spacing^ as for kaolinite. Halloysite, therefore, can be identi- fied by the greater spacing in X-ray diffracto- grams of samples containing natural moisture.

Nonclay minerals and other impurities in hal- loysite vary considerably in different deposits. Some deposits, such as those in the Dragon mine, Utah, are exceptionally pure and .contain only minor quantities of contaminants, con- sisting chiefly of pyrite, silica, dolomite, iron- bearing minerals and noncrystalline materials, and manganese oxides (Morris, 1968). In most deposits, silica is the principal impurity: it oc- curs in the form of quartz, cristobalite, chert, and poorly crystalline forms. Many halloysite deposits are intermixed with kaolinite, and sev-

era1 in western United States are closely asso- ciated with alunite. Gibbsite and manganese minerals also occur in some halloysite deposits.

Occurrence and Origin-Small deposits of halloysite occur at many places in the United States, but known deposits large enough to mine profitably are rare. The deposits in the Dragon mine, Utah, the major producer, are two large pipelike bodies replacing lower Palrxoic lime- stone near the contact with monzonite porphyry (Kildale and Thomas, 1957). The two bodies are separated by a zone of iron-oxide deposits extending along the Dragon fissure (Morris, 1968). The occurrence of these deposits and the minerals associated with them clearly indi- catc that they formed by hydrothermal activity. Other deposits thought by Papke (1971) to have formed hydrothermally occur in the Ter- raced Hills, Washoe County, Nevada. These deposits are bedded and apparently altered mainly from tuff. The halloysite in the Gore district, Georgia, is bedded and occurs in the Armuchee Chert of Devonian age (Broadhurst and Teague, 1954). An adequate explanation of these deposits has never been advanced, but the extent of the beds suggests that they are of sedimentary origin. Halloysite mixed with ka- olinite in the Spruce Pine district, North Caro- l ina (Hunter and Hash, 1953; Parker, 1946), and the Bovill district, Idaho (Hosterman et al., 19601, is mainly residual and formed by the weathering of igneous rocks. Several de- posits in foreign countries are thought to have formed hydrothermally, and some are the re- sult of surficial weathering. ..

Distribution of Deposits: United States- Virtually all major productive halloysite de- posits in the United States have been referred to in the foregoing discussions. Most of the many other known scattered deposits are either too small or too impure to he considered as significant sources of halloysite. Possible ex- ceptions include the following: ( 1 ) the halloy- site mixed with kaolin in weathered nepheline syenite masses in the Arkansas bauxite region (Gordon, et al., 1958); (2 ) the body of halloy- site reported to have been exposed for 350 ft in the adit of a mine in the Bullion (Railroad) district, Nevada (Olson, 1964); and (3) rather extensive deposits reported near Bartow, GA (Anon., 1959). Possibilities for the discovery of new large high-grade deposits are not easy to evaluate. The likelihood of major discoveries does not seem promising, but rocks in many large areas in western United States have been altered hydrothermally, and seveial of these could contain large deposits of halloysite. Also,

Industrial Mine ~. 636

resources of halloysite in the old Gore mining district in Georgia are estimated at more than a million tons (Broadhurst and Teague, 1954). and some use may again be found for these deposits.

Olher Countries-Halloysite occurs in many countries, but, as in the United States, most deposits are small; the authors are aware of small-scale mining only in Morocco, Japan, Korea, Czechoslovakia, and New Zealand. The deposits mined in Morocco are in the Maaza district about 6 km west of Melilla (Hilali et ai., 1969; Martin Vivaldi and Vilchez, 1959). These deposits occur above travertine and are overlain by pyroclastic materials. They are in a bed of Pliocene age, ranging in thickness from 1.5 to 2.5 m. Halloysite mined in Japan in- cludes deposits that formed by hydrothermal alteration of granite and quartz porphyry and others that were transported and deposited in sedimentary basins (Takeshi and Kato, 1969). Hydrothermal deposits occur at the Taishu mine, and white sedimentary halloysite is in the Tajimi and Arikabe deposits. The halloysite mined in Korea is presumably from the San Chong and Tan Song deposits described by Kim and Kim (1964). The halloysite deposits mined in Czechoslovakia are in the Michalovce district in the eastern part of the country (Kuzvart, 1969). These deposits are thought to have formed by the hydrothermal alteration of da- cite. They extend over an area 500 m square and are as much as 36 m thick. They occur below overburden 30 to 40 m thick. The halloy- site mined is reported to be suitable for use in ceramics, refractories, paper and rubber fillers, and in refining sugar. The deposits in New Zealand occur in the Maungaperua district on the North Island. This clay is mined by New Zealand China Clays, Ltd., and sold for use in paper filler, ceramics, paint extenders, and filler for adhesives and cosmetics. The halloysite is in massive deposits formed by hydrothermal alteration of andesite of middle Cenozoic age (Bowen, 1969).

Several of the kaolin deposits in other coun- tries consist of mixtures of halloysite and ka- olinite. One such mixed deposit occurs in altered felsitic volcanic rocks in the Burela dis- trict, Spain (Anon., 1972b), the principal kaolin-producing center in that country. The kaolin produced contains appreciably more hal- loysite than kaolinite, but the clay must be con. sidered to be a mixed type. Another mixed halloysite-kaolinite deposit is in the Bukidon district in the Philippines (Comsti, 1969).

Future Considerations and Trends: Halloy.

lis L-?

site will probably be in demand in the UnitG ' ' States for use in petroleum catalysts and 0 t h products as long as suitable high-quality d e -. posits can be mined at a reasonable cost. h - mentioned previously, known high-grade +, 1 posits are limited, and though additional &. . posits may be found, the point may be reached :$

when it will be cheaper to use substitute m- - terials than to prospect for new deposits. Caw -

lysts made from halloysite are in competition -. with those manufactured from kaolin and syn. thetic materials containing alumina and siliu

The products other than catalysts made from halloysite' in recent years are all low-value or. : high-weight items lacking the broad market bau : of catalysts. All these other products can bc made from other clays or other materials, but halloysite will continue to be, used for them until reserves are exhausted, cheaper substitute found, or.loca1 markets disappear. ..

Refractory Clays

'.A:; . . . . 1 . 41. ., .

. . , , ;~ , . .,.--:; .A,.. , . History and Uses: The first plant in Ihr

United States for making refractory producu from clays began operation at Salamander, NJ. in 1825. The refractory industry grew rapidly and expanded from New Jersev to cenlen in Pennsylvania, the Ohio River valley, Missouri. and to western states.

Refractory clays are used mainly in making firebrick and block of many shapes, innulatin8 brick, saggers, refractory mortars and mixu monolithic and castable materials, ramming and air gun mixes, and other products. A produa called chomottes in Europe (Anon., 1972. 1972i) and elsewhere is made by calcinin8 high-grade fire clays and other kaolinitic c la j l A similar material produced in the United States is called merely calcined clay or calcined kaolin. A related material called mullite refrac- tory is made by calcining bauxitic clay or claYeY bauxite. Further fabrication into finished fractory products is required for chamottes and calcined clay. Considerable tonnages of fife clay also have been used in the past in * United States in the manufacture of li@ colored face brick, tile, stoneware, and olhu products.

Product Specifications: The specifications for refractory clays are as many as the differen* uses. As resistance to heat is the most esrenod property, many specifications include referew to pyrometric cone (Table 4), indicating tbc heat duty required. Resistance to shrinkage. warping, cracking, and abrasion is alSo veT). important in many products, and exPmionr of the requirements for these properties

in some specil ucts must full sions. Restric clude cutoffs content of alk constituents th

Geology: 7 origin of refra clay have beer tions. Therefo be concerned ' apply to fire cli

Mineralogy- kaolinite, the varies considez the harder and clay) is very w perfectlycrysta kaolins. The I;: tends to occur harder varieties kaolinite in thc however, is ord fectly crystallir ordered form o referred to as 10 distinguish it ked forms.

Some of the t Contain mineral. than kaolinite, : products can be fractory kaolin gibbsite, A120;: clay, that are e: consist of kaolil and minor quan

Occurrence a, acteristics of fir, clays range fror, Fire clay, there semiplastic. semi has unique prop ticity, breaks wi shardlike particle limestone. Typic hard and has a1 texture. Such c birdseye, or nod

Most fire clay and deposits ran: to Tertiary. Fire in rocks of Penn this age occur as mediately below , beds. Fire clay o Occurs mainly in

st plant in tk actory produilr ialamandcr. & J , ry grew rapid:; :Y to centers i.2

.alley, Missot:r!.

ainly in maiinp tapes, insulailnr !ars and mixc). Is, ramming an& acts. A product (Anon.. 1'1.2.

IC by calcininy kaolinitic cia!,. in the Unitc:!

clay or calcincd i mullite r c f r a ~ . ic clay or c l a y < i t0 finished rc- r chamottes a d Innages of f i re ;he past in the cture of ligh!. rare, and other

pecifications f o r as the differen! e most essential d u d e refercncc

indicating thc : to shrinkasr. ,n is also VCP' md expressiol" aperties a p P r

Clays 637

fications on dimen-

he degree of ordering of the ncipal mineral in fire clay, y. Most of the kaolinite in

Some of the better grades of refractory clays contain minerals that are richer in aluminum than kaolinite, and, therefore, higher alumina products can be made from them. Some re- fractory kaolin is a mixture of kaolinite and gibbsite, AI,0,.3H2O. The better grades of fire clay. '&hat are exceptionally rich in alumiwm, comist of kaolinite and diaspore, -A130;H,0,

acteristics of fire clay vary considerably; the clays range from soft and plastic to flintlike. Fire clay, therefore, is divisible into plastic, &plastic, semiflint, and flint types. Flint clay has unique properties for a clay; it lacks plas- ticity, breaks with a conchoidal parting into shardlike particleg, and most of it is as hard as

age, and deposits of ys (seat earths) im- associated with coal- us and Tertiary age

curs mainly in lenticular bodies. Some de-

. .

posits of these ages are associated with lignite and are probably underclays, and others have apparently been transported and deposited in local basins in a nearshore, swamp, or flood- plain environment.

Opinions differ considerably on the origin of the extensive fire clays occurring below coal- beds. Some geologists (Keller, 1970; Patterson and Hosterman, 1963), including the authors, believe that most underclay deposits formed mainly by the alteration of aluminous sedi- ments in a swampy environment. Some min- eralogists, however, believe that these clays were transported and some sort of a sedimen- tary winnowing process caused the rather pure accumulations of kaolinite in fire clay. Some clays of Cretaceous and Tertiary age have been transported and formed by a process similar to those thought to have formed the transported kaolin deposits.

Distribution of Deposits: Unired Smes - Fire clay of Pennsylvanian age is widely scat- tered throughout the Appalachian region and parts of the Mississippi Valley (Anon., 1967). The very high quality diaspore-bearing clay, as well as other grades of fire clay, occur in the Clearfield district, Pennsylvania (Anon., 1964; Bolger and Weitz, 1952) (Fig. lo), and the Ozark region in Missouri (Keller, 1952; Keller et al., 1954). High grade kaolinitic flint clay and semiflint clays are mined in the Olive Hill district, Kentucky (Patterson and Hosterman, 1963); Oak Hill district, Ohio (Stout, et al., 1923) ; and Somerset district, Pennsylvania (Hosterman, et al., 1968). Major districts pro- ducing fire clay suitable for low- and moderate- heat-duty refractory products include the Al- legheny Valley and Beaver Valley districts, Pennsylvania; Cordova district, Alabama; East Liverpwl district, Ohio and West Virginia; and the Tuscarawas Valley and Hocking Valley dis- tricts, Ohio (Hosterman, et al., 1968); and a region including parts of Monroe, Audrain, Callaway, and Montgomery Counties, Missouri (McQueen, 1943).

The largest and best quality fire clay deposits in the Rocky Mountain region are in Fremont, Pueblo, Custer, Huerfano, Jefferson, and Las Animas Counties, Colorado. These deposits are in the Purgatoire Formation and Dakota Sand- stone of Cretaceous age (Waagi, 1953). Fire clay in these deposits occurs as isolated tabular lenses ranging in thickness from 3 to 20 ft.

In addition to the fire clay mentioned in the foregoing discussions, other deposits are scat- tered throughout the western states (Anon., 1967; Mark, 1963; Van Sant, 1959, 1964).

_ -

i

638

These deposits are of several types, and they include transported, residual, and hydrother- mally formed clay. Districts in which these scattered deposits occur include several areas in King County and the Castle Rock area in Cowlitz County, Washington, the Molalla and Hobart Butte areas, Oregon; and the Alberhill area, California. Most of these deposits are of Cenozoic age.

Refractory kaolin is produced primarily in the following districts: ( I ) Georgia-South Caro- lina kaolin belt; (2) Andersonville, Georgia (Anon., 1972a); ( 3 ) Eufaula, Alabama; (4) Arkansas bauxite region; ( 5 ) scattered districts in Texas; ( 6 ) Latah County, Idaho; and (7) Ione, California (Anon., 1972e). Refractory ball clay is produced primarily in the western parts of Kentucky and Tennessee, but some of the ball clay produced in Texas may be used in refractory products.

The total refractory clay. resources in the United States suitable for 1ow:heat-duty refrac- tory products may be as much as 1 billion tons (Hosterman, 1973). However, the reserves- those clays that can be mined and processed now at competitive costs and are suitable for low-heat-duty products or better-are probably no more than 1 billion tons. The reserves are primarily in the fire clay and refractory kaolin and ball clay districts outlined previously. The remaining resources of high-grade diaspore clay are mainly under considerable overburden in Pennsylvania, and only small resources are pres- ent in Missouri. The bauxitic kaolin resources are primarily in the Arkansas bauxite region, and the Eufaula, Alabama, and Andersonville, Georgia, districts. Some deposits also occur in other parts of Alabama and Georgia.

Other Countries-Refractory clays are pro- duced in many countries; however, the informa- tion available to the authors on worldwide pro- duction is sketchy and incomplete. This is partly because the distinction between fire clay and miscellaneous clay is not made in some countries, and clay used for refractory prodocts is lumped with kaolin in others.

Those countries that produce more than I million tons of refractory (fire) clay annually include the United Kingdom, Federal Republic of Germany (West Germany), and Japan. The production in France exceeded a million tons a few years ago but has apparently dropped be- low this figure in recent years. Other countries producing 100,000 to 1 million tons annually include Argentina. Australia, India, Italy, Mexico, New Zealand, Sweden, the United Arab Republic, Uruguay, and Yugoslavia. Re-

. ~. \ , . . -,. ;i

fractory clay is exported from the Peoples Re- :.:I public of China, which is apparently a major 2; producer. Fire clay is also mined in the USSR, 4 Czechoslovakia, Hungary, Poland, and other. , East European countries. . . . ' ,.,--. Tz,>*'+<!

As in the United States, fire clay in other '2 countries is in several types of deposits. Ka- olinitic fire clay associated with coalbeds of -< Carboniferous age is mined in the United King- .$ dom, France, Federal Republic of Germany, 7

1 and elsewhere. Very high alumina diaspore- bearing flint clays are sources of refractory ma- terials in Scotland, South Africa, Israel, and the Peoples Republic of China. Refractory kaolin 2 is mined in Japan, India, Hungary, Italy, '.$ Czechoslovakia, Poland, Sweden, Yugoslavia. -.> Mexico, Argentina, Brazil, Chile, Peru, Repub- lic of South Africa, United Arab Republic.. _I Australia, New Zealand, Iran. and other coun- I

~. 2

tries, and most such deposits are no older than . -. . CretaGeous. . , . . '

used in exploring and evaluating fire clay de- posits are in general similar to those used for bentonite and kaolin, except that different drill- ing and testing procedures are required. Drill- ing fire clay deposits, particularly those of Pennsylvanian age, ordinarily requires diamond bits and core barrels of the type used for min- erals in hard rock. This is because the clay itself and the rocks overlying the deposits arc hard. The most common test in the evaluation of fire clay is the determination of PCE ( p y r p

metric cone equivalents, Table 4, p. 613). In addition to the PCE requirement, fired tal

pieces also may be tested for such properties as high-temperature stability, hot strength, poror- ity, and spalling (Anon., 1972h; Norton, 1968), Chemical analyses are. also required for Some evaluations, and the contents of alkalies, alka- line earths, iron oxides, and a few less common elements are critical. because they act as flux= when clay refractories are heated;

Preparation for Markets: Fire clay and other refractory clays are mined by methods similar to those used for other types of clay. However. a much higher percentage of fire clay mining in the past has been underground. The under- ground mining has been required because much of the higher quality clay occurs at consider- able depths, and the overlying rocks are '00

Firebrick and related products are prepared for markets by grinding the clay, shaping Or

forming the firebrick or other products, and fir- ing. Commonly several varieties of fire clay and grog (crushed previously fired clay) arc

Exploration and Evaluation: The method;'

. -:.

.. . hard to strip profitably. . . .

blended to mak product, and bli prepare differen clays are ordina they lack plastic or plastic fire cl forming and b, Most firebrick i! mechanical pres U C ~ S are intricati by hand.

Most firebrick by gas or oil. P making speciall! limited market. products are pal truck. Heavy cr required for ove is ordinarily fire1 in both paper ba

Future Consid output of refrac States was 1 I .S tion has decreasi versals of the tri the total refract1 lion tons valuec This trend in dec has been due ma ( I ) the develop nous refractory I basic oxygen pro quires basic raths irfurnaces; ( 3 ) < whereby fire cla brick. stoneware. classified as m i x clay. .

The decrease i i brought about b previous paragrai and markets for made from it cat sistently. Deman in the year 200 17 million st (C,

The availobilit: grade refractory one of the long- refractories indu grade diaspore c souri that can bi are nearing exhai ing increases cos underground min the production c olinitic clay has i

Peoples R ~ . -n tb a major in the USSR, 4 and other

clay in . other deposits. Ka. 1 coalbeds 01 : United King. of Germany,

h a diaspore. refractory ma. Israel, and the ractory kaolin Jngary, Italy,

Peru, Repub. TahRepublic. Id other twin. no older than

The methods 3 fire clay de. :hose used for different drill- quired. Drill. arly those of luires diamond used for min-

:ause the clay le deposits arc the evaluation ,f PCE (pyro. , p. 613). ment, fired test h properties ar trength, poros. *Torton. 196s) iired for some alkalies, aha-

v less common :y act as fluxe,

clay and other tethods similar :lay. However. re clay mininc d. The under- because much

rs at considcr- rocks are 100

s are prepared ay, shapins or 0ducts;and fir- 2s of fire clay ired clay) arc

1, Yugoslavia,

-

Clays 639

: blended to make a mix desired for a certain product, and blends are varied considerably to - prepare different grades of firebrick. The harder clays are ordinarily the most refractory, and as they lack plasticity, small proportions of kaolin . or plastic fire clay or both are added to aid in

, forming and bonding the brick until firing. .-.Most firebrick is formed by hydraulic or other I 'mechanical presses, but several types of prod- .. ucts are intricately shaped and must be formed

firebrick is fired in tunnel kilns heated .. by gas or oil. A few plants, particularly those

making specially shaped products or having a limited market, use downdraft kilns. Finished products are palletized and shipped by rail o r truck. Heavy crating with padded packaging is required for overseas shipments. Calcined clay

Future Considerations and Trends: The peak output of refractory (fire) clay in the United

s 11.8 million tons in 1957. Produc-

rather than alumina-type firebrick

ase in demands for refractory clays ut by the factors outlined in the graph has probably bottomed out,

and markets for refractory clay and products made from it can be expected to increase con- sistently. Demands forecast for refractory clay in the year 2000 are expected to be 12 to 17 million st (Cooper. 1970).

The availability of high-grade and very high grade refractory clays at competitive costs is one of the long-range problems faced by the refractories industry. Deposits of very high grade diaspore clay in Pennsylvania and Mis- souri that can be mined by stripping methods are nearing exhaustion, and underground min- ing increases costs considerably. The cost of underground mining is one of the reasons why the Droduction of refractorv bauxitic and ka-

G A and Eufaula, AL, districts in recent years. The trend for thr increasing use of these baux- itic clays is expected to continue. Another trend may be an increase in the heneficiation of kaolin both to improve purity and to re- cover a coproduct, such as glass sand;to make the cost competitive. Kaolin and glass sand are now produced as coproducts from impure de- posits in Texas, Idaho. and Califor.nia. ' . . '

' Miscellaneous Clay and Shale Miscellaneous clay and shale includes a wide

variety of clay and other fine-grained rocks that are used in many ways. Most products made from them are fired and include such things as structural and face brick, drain tile, vitrified pipe, quarry tile, flue tile, conduit, pottery, stoneware, and roofing tile. Very large ton- nages of these materials are bloated by firing to form lightweight aggregate, and large quanti- ties are used in making portland cement (see the specific chapters in this volume). Uses not requiring firing of a finished product include filler for paint and other products and shale and clay used for packing dynamite in blast- holes and for plugging oil and gas wells that are no longer in use. Adobe building blocks are also used in unfired form in several south- western states:

Properties

Clay and shale are used in so many different structural clay products that they necessarily have a wide range in physica1,properties. The properties are plasticity, green strength,. dry strength, drying and firing shrinkage, vitrifica- tion range, and fired color. The properties de- sired vary with the structural clay product made. For .example, a clay used in making conduit tile must be very plastic and have high green and dry strengths and uniform shrink- age, but for drain tile or common brick these properties do not have to be controlled so closely.

Most clays are plastic when naturally wet or mixed with water. Plasticity can be defined as the property of a material to undergo perma- nent deformation in any direction without 'UP- ture under stress beyond that of elastic yielding. Some clay materials are very plastic and are called fot clay; others having little plasticity are called lean clay. The type of clay mineral, particle size, particle shape, organic matter,' soluble salts, adsorbed ions, and the amount and type of nonclay minerals influence the plastic properties .~ of clay.

640 ~. Industrial Minerals a n d Rocks

Green-strength and dry-strength properties of clay and shale are important because most structural clay products are handled at least once and must be strong enough to maintain shape. Green strength is the strength of the clay material in the wet or plastic state. Dry strength is the strength of the clay after it is dried. Plasticity and green strength are closely related and are influenced mainly by the same variables. Dry strength is dependent on the proportion of fine particles present, the shape of the individual particles, the degree of hydra- tion of the clay fraction, the method of form- ing the ware, and the rate and thoroughness of the drying. The presence of a small amount of smectite, which occurs in very fine hydrated particles, generally increases dry strength.

Both drying and firing shrinkages are critical properties of clay used for structural clay prod- ucts. Shrinkage is the loss in volume of a clay as it is dried or fired. Drying Shrinkage is de- pendent on the water content, the character of the clay minerals, and their particle size. Most plastic clays shrink appreciably with drying, which tends to produce cracking and warping. Sandy clay or clay having low plasticity has low shrinkage properties but tends to produce a weak porous body. Smectite minerals in ra- ther large amounts (10-25% ) commonly cause excessive shrinkage, cracking, and slow drying. Firing shrinkage depends on the density of the clay, volatile materials present, the types of crystalline phase changes that take place dur- ing firing, and the dehydration characteristics of the clay minerals.

The temperature range of vitrification or glass formation during firing is a very impor- tant property of clay and shale used in struc- tural clay products. Vitrification is a process of gradual fusion in which some of the more easily melted constituents produce increasing amounts of liquid as the temperature is increased. This liquid produces glass as the material is cooled, and the glass is the bonding material in the final fired product. Some clay has a shon vitrifica- tion range, and when such clay is fired the temperature of the kiln must be very closely regulated. Clay consisting chiefly of illite, smectite, or chlorite has lower vitrification tem- perature than kaolinite-rich clay. Some mineral impurities in clay, such as calcite and feldspar, lower vitrification temperatures by acting as fluxes. The degree of vitrification attained also depends on the duration of firing and the tem- perature. Commonly the degree of vitrification is regulated by the amount of shrinkage and porosity needed in the final product.

Uniform color is an essential pro many Structural clay products. The color of a product is influenced by the state of oxidation and particle size of the iron minerals; the firing temperature and degree of vitrification; the portion of alumina, lime, and magnesia in the clay material; and the composition of the gasa in the kiln during the burning operation. High. grade white-burning clay contains less than 1 % Fe,O,, buff-burning clay ordinarily contaim 1-5% Fe,O,, and red-burning clay contaim - 5% or more Fe,O,. Other constituents also affect the color, but finely divided iron-bearing ' - minerals generally are the principal causing color in fired products.

Occurrence _,. ,.

Miscellaneous clay and shale occur in^ many types of rocks'ranging in age from Precambrian lo Holoqene. They include glacial clay, soils. . alluvium, loess, shale, weathered and fresh schist, slate, and argillite. Some fire clay and kaolin are also included in the miscellaneous clay group, particularly when used in the manu. facture of structural-clay products. This group consists of so many different types of rocks that only a few broad generalizations about their mineral makeup are possible. The most com- mon mineral in many of them is one of the members of the mica group, and the dominant one in a given deposit may be illite, sericite, or one of the micas normally occurring in coarser grain sizes, such as muscovite and biotite. In addition to illite, the clay minerals present com- monly are kaolinite, smectite, mixed-layer vp rieties, and chlorite, Some materials in this group actually contain more quartz and other

Miscellaneous clay and shale are now mined'

. '

.~

-

.- ' .-. -

detrital minerals than clay minerals. . < . -:

in every state in the United States, except Alaska and Rhode Island, according to us Bureau of Mines Minerals Yearbooks. In 1980. 32.4 million tons of these materials having a value of $ 1 14.7 million was produced (Table 1). The states producing more than 1 million ton' were Alabama, California, Georgia, Illinois. In- diana, Iowa, Louisiana, Maryland, M i c h i p , Missouri, New York, North Carolina, ohto. Pennsylvania, South Carolina, Texas, and W- ginia. Texas was the leading state in production in 1980, with 3.4 million tons, and North Caro- lina was second, with 2.8 million tons. . .-,.

-

'

Testing, Processing, and Markets . , . The testing of miscellaneous clay and shale

for most products requires the preparation Of

test pieces of spe( firing (Clews, 196 felter and Hamlin. tested for such pr ing, cracking, perm crushing or compr soluble salt contenl products.

Miscellaneous c open pits, Pits m digging must be c material and finish the margin of prc products made fro essed and . markei described for refra

Future Consideratii

The long-range I products made f n shale can be expe, growth in the gror mands for others a growth rate. Dem, quired for portland gregate are increas to continue. Thou: tural-clay 'products rials are facing stroi wood, glass, plastic als. Growth in d products is also.har of these products, range, and by incre rise in fuel costs, seems likely to be the industry. . ~.

Another strong I miscellaneous clay to rural areas. Fo near population cei tion costs. Suburb: tion centers has f r relocate because o raw-material supply certain to continu plants are in rural to favor a substiti creased transportat.

Government C. Bentonite and Kaol

resources in the domain lands. At

Most of the bent

property The color of Le of oxidation .=Is: the firing lation: the pro. Wnesia in the on of the ease, 'eration. High. 5 less than I 2 larily contain,

clay contain5 'nstituents a150 :d iron-bearinp cipal material,

W r in many n Precambrian i a l clay, soil,, :ed and fresh : fire clay and

miscellaneou\ d in the manu. Is, This group :s of rocks thsl ns about thcir 'he most coni- is one of thc

I the dominant .ite, sericite. or ring in coarser md biotite. I n 1s present coni- lixed-layer c - Nterials in thi, art2 and othcr 11s. ire now mined States, exccpi 3rding to LS O D ~ S . In 19SO. rials havin? 3 iced (Table I ). 1 million tons ia, Illinois, In. nd, Michigan. arolina, Ohio. exas, and Vir. : in production d North C a m tons.

i

:lay and shale ?reparation of

9' test pieces of specific dimension. drying, and firing (Clews, 1969; Grimshaw, 1972; Kline- feller and Hamlin. 1957). Fired test pieces are tested for such properties as shrinkage, warp- ing. cracking. permeability, modulus of rupture. crushing or compression strengths. Color and soluble salt content are also important for some products.

Miscellaneous clay and shale is dug from 'open pits. Pits must be near plants and the

digging must be cheap, because both the raw material and finished products are heavy, and

' the margin of profit is ordinarily low. Most : products made from these materials are proc- ' essed and 'marketed much in the manner i described for refractory clays.

. Future Considerations and Trends

7

k i

The long-range trends in demands for some products made from miscellaneous clay and shale can be expected to keep pace with the growth in the gross national product, but de- mands for others are likely lo fall short of this growth rate. Demands for clay and shale re- quired for portland cement and lightweight ag- gregate are increasing, and this trend is likely to continue. Though demands for heavy struc- tural-clay products will continue, these mate- rials are facing strong competition from cement. wood, glass, plastics. aluminum and.other met- als. Growth in demands for structural-clay products is also hampered by the heavy weight of these products, which limits their market range, and by increasing production costs. .The, rise iin fuel costs, which has been forecast,

... seems likely to be a major problem faced by the industry.

Another strong trend in the industry using miscellaneous clay and shale has been the shift lo rural areas. For a long time, plants were near population centers because of transporta-

, tion costs. Suburban growth in many popula- tion centers has forced plants to close or to relocate because of ecological pressures and

, raw-material supply problems. This trend seems certain to continue until virtually all active plants are in rural areas, which, in turn, tends to favor a substitute material because of in- creased transportation costs and other factors.

- Government Controls and Influences = Bentonite and Kaolin on Public Domain Lands

Most of the bentonite and part of the kaolin ources in the United States are on public main lands. At the time this chapter was

written, bentonite and kaolin deposits on fed- eral lands for which mineral rights were not withdrawn or otherwise not obtainable were subject to the general mining laws. Mining claims could be filed on valid bentonite de- posits, and under certain conditions such claims could be patented. The staking and patenting of mining claims on public domain lands are primarily under the jurisdiction of the Bureau of Land Management, an agency of the US Department of Interior. Further information on the staking and patenting of mineral claims on federal lands can be found in Bureau of Land Management pamphlets 0-377-927 and 0-3 77-93 0.

Depletion Rates The following depletion rates were in effect

in 1973 (Anon., 3972k): kaolin, ball clay, bentonite, fuller's earth, and fire clay, 14% domestic and 14% foreign; clay and shale used for making brick, tile, and lightweight aggre- gate, 7 % % , both domestic and foreign. The depletion rate for clay used for the extraction of alumina or aluminum compounds was set at 22%, but because'no clays have yet been used for this puropse in the United States the rate was not applied.

Tariffs

The statutory rates of duty per long ton for the various classes of clay in effect in 1980 (Ampian, 1981) are listed in Table 5.

Ecology All segments of the clay industry, like all

other mineral industries, face major problems related lo the environmental controls, and com- pliance with regulations now in effect has added significant production costs. Virtually all the major plants producing clay involving a dry- grinding process have installed equipment to control dust emissions in the atmosphere. Not all such equipment has proved effective, and some companies are faced with further expendi- tures for improving dust control. The control of turbidity and other contamination in water pumped from pits and discharged from wash- ing and other types of plants is also required. This regulation has forced mining to be shut down at least temporarily in flooded fuller's earth pits and adds the costs of maintaining settling ponds to remove the suspended mate- rials in the discharge from kaolin-washing plants. As most clays are strip mined, land

- -.

642 - Industrial Minerals and .Rocks

1 TABLE 5-Tariffs per Long Ton for Variws Classes of Clay. 1380 i.. ' : ,:+ + ~ j .,

Rate of Duty (per Long Ton. $1 .. v

. ,,~~. ...I .; Item Nan-MFN ' TSUS Number Most Favored Nation (MFN) - __

111181 1/1/87 . . ..: ; ' i i imi . 33.0g -._. - $2.50

Wholly or partly beneficiated 521.54 50.0$ 50.0$ ~.,.- 3.25 Bentonite 521.61 40.0$ 40.0P . . 3.25 :

; .1.w - Ball clays. not beneficiated 521.71 41.0$ 38.0$ Wholly or partly beneficiated 521.74 ' 83.0.g 77.0$ . '.I :. . 2.00

Other clays, not beneficiated 521.81 Free Free ' . 7 ' c ' ' ! . 1.00

-. China clay and kaolin 521.41 33.0$ Fuller's earth, not beneficiated 521.51 25.0$ 25.0$ .. ' 1.50

. .

Wholly or partly beneficiated 521.84 50.0$ ' 50.0$ :.'. . .,. - . 2.00 1

reclamation costs are now a major item. Com- monly, as much as $500 per acre is spent in restoring mined bentonite lands in Wyoming, where the value for the surface alone is only ahout one-tenth of that amougt. The restora- tion of some of the strip-mined land in the Georgia kaolin belt costs as much as $800 per acre, hut the average cost is ahout $300 per acre. The high costs of reclamation in Georgia are due to state laws governing mining that are even more stringent than the federal regulations.

Acknowledgments

Much of the authors' knowledge of the vari- ous clay industries has been gained by conver- sations and other communications with many professional and management personnel. Sev- eral of these persons contributed to the infor- mation required by one or both of the authors for the preparation of this chapter, and others have aided them by contributing to their gen- eral background knowledge in the past. Among those to whom we wish to express thanks are John McKenzie and Kefton H. Teague of Inter- national Minerals and Chemical Corp.; William T. Granquist and John W. Jordon of NL In- dustries; Arthur G. Clem and E. P. Weaver of American Colloid Inc.; W. L. Otwell, D. B. Crosten, and T. E. ShuWebarger, Jr., of Penn- sylvania Glass Sand Corp.; Finus Turner of Dresser Magcohar; Jack W. Williamson, W. L. Haden, Jr., and T. D. Oulton of Engelhard Minerals and Chemicals Corp.; lames L. Rod. gers of Georgia-Tennessee Mining Co.; R. C. Valenta and Richard M. Jaffee of Oil Dri Corp. of America; Robert P. Smith, Waverly Mineral Products Co.; J. F. Bunt and Glen P. Jones of General Refractories Co.; J. F. Wescott of A. P. Green Refractories; Edward Ruh and

. .... .,. -_ : 1

0. M. Wickem of Harhison-Walker; P. E. 'i Turbett and H. C. Spinks of Clays Corp.: D. W. L. Spry, Clive W. Gronow, and.William Mallory of Anglo-American Clay Co.; James D. Cooper .and Sarkis G. Ampian of the US. Bureau of Mines; Jack Rogers, E. E. Oxford. Tijs Volker, and Ralph B. Hall of I. M. Huber Corp.; R. V. Colligan, Fred Gunn, H .H. Mor- ris. Paul Sennet, James Olivier, and Robert Weaver of Freeport Kaolin Co.; Paul Thiele and Owen Etheridge of Thiele Kaolin Co.: Wayne M. Bundy. John M. Smith, and Dora1

-Mills of Georgia Kaolin Co.; George Eusnei of Mulcoa-CE Minerals; R. E. Grim, University of Illinois; W. D. Keller and W. D. Johns, Uni- versity of Missouri; George W. Brindley and Thomas F. Bates, Pennsylvania State Univer- sity: William F. Bradley and Edward Jonas! University of Texas; C. E. Weaver and W. E. Moody, Georgia Institute of Technology; John Koenig and Malcolm McLaren, Rutgers Uni- versity; N. 0. Clark and C. M. Bristow, English China Clays; B. F. Buie, Florida State Univer- sity; and Walter Parham, Minnesota Geological Survey.

Consulting geologists and engineers who have assisted the authors in many ways include Thomas L. Kesler, W. B. Beaty, Padriac Part. ridge, E. W. Adams, Richard H. Olson, G. w. Phelps, William J. Lang, Richards A. Rowland. and Wayne Fowler.

The authors were also aided in the prepara- tion of this chapter by having access to infop mation gathered by John W. Hosterman (1973) during the preparation of the clay chapter in an overall review of the mineral resources of the United States published by the US Geological Survey. E. C. Freshney of the U.K. Institute Of Geological Sciences supplied references to ma- terial on some of the clay deposits in'the United Kingdom discussed in the previous pages,

.

. ..

M. Kuzvart of C ganized the Kai International Gel which much of kaolin deposits Ciudad Universi the AIPEA Mer provided inform Spain. R. E. G manuscript and t gestions. K. Y. a report on whk the Peoples Repi

Eibliogral,

Anon., undated, Technical Bulle

Anon., 1952, Mar! frocrory Maren Society for Tesi

Anon., 1958. "Ble Method. Cc 8a ciety. 2 pp.

Anon., 1959, "Ha trict: Georgia Geological Surr

Anon., 1962, "Br: p. 244.

Anon.. 1962a. M G American Foun 619 pp.

Anon., 1963, Fori American Foun 200 pp. .'

Anon., 1964, "Ma ' lacent Units in

Counties, Pen" Pennsylvania GI

Anon., ,1965, "B Trade Nora. I No. 4, pp. 12-14

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Anon.. 1969a. "i Drilling Fluid

15 PP.

.. . ._ .

$2.50 1.53 3.25 3.25 1.00 2.00

2.00 -. 1.00

I-Walker; P. E.

OW, and William ay Co.; James D. i a n of the us s, E. F. Oxford. I Of 1. M. Hubel. unn, H .H. Mor. ier. and Roberl 30.; Paul Thielr ele Kaolin Co.: h i t h , and Domi jeorge Eusner iil ?rim, Univsrsii! 1. D. Johns. Uni- W. Brindley and iia State Uniwr- I Edward Jonar. eaver and W. E. rechnology; John :n, Riitgers Uni. Bristow, English

ida State Uniwr- iesota Geologic:tl

,gineers who haw iy ways inclodc aty, Padriac Parl- H. Olson, G. \<.

iards A. Rowland.

:d in the prepara- g access to infor. Hosterman (19731 clay chapter in a n I resources of Ihc he US Geological : U.K. Institute @ f references to m - osits in the U n i d

previous p a P

, U l a y s Corp.:

Clays

M. Kuzvarl of Charles University, Prague, or- ganized the Kaolin Symposium at the 23rd International Geological Congress in 1968 from which much of the information on foreign kaolin deposits was taken. Martin Vivaldi, Ciudad University, Madrid, Spain, organized the AIPEA Meeting of 1972 and personally provided information concerning the clays in Spain. R. E. Grim and B. F. Buie read the manuscript and both made several helpful sug- gestions. K. Y. Lee translated the sections of a report on which the discussion of kaolin in the Peoples Republic of China is based.

$ .!- - ..

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[i -

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~ ~. ~~~ ~ ~ ~

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