Muessig and Allen-1957

EZCURRITE (2Na,O.5B,Os.7H,O), A NEW SODIUM BORATE FROM ARGENTINA: OCCURRENCE, MINERALOGY,

AND ASSOCIATED MINERALS •

SIEGFRIED MUESSIG AND ROBERT D. ALLEN

CONTENTS

PAGE

Abstract .............................................................. 425 ,

Introduction .......................................................... 427

Geology .............................................................. 428 Regional setting .................................................... 428 Mine area .......................................................... 428

Borax deposit ...................................................... 428 Mineral occurrences ................................................ 429

Mineralogy ........................................................... 431 Optical properties ................................................... 432 X-ray data ......................................................... 433

Chemical analyses ..................................................... 434 Differential thermal analyses ............................................ 435 Discussion ............................................................ 435 References ............................................................ 437

Ezcurrite (2Na•O.SB20,.7H,O) is a new sodium borate mineral discovered at the Tincalayu borax mine in the Province of Salta, Argentina. The mineral is associated with borax and kernite; ulexite and inderite also occur in the borate sediments. Tincalconite occurs as a weathering prod- uct of borax. Ezcurrite looks like kernite and has the following properties: Sp. Gr. = 2.153; ns (Na) •x = 1.472,/• = 1.506, • = 1.526; biaxial negative; 2V (calc) 73•ø; Z /X elongation 42.6 ø. It contains: B=Os, 58.21%; Na:O, 20.73%; H20, 21.06%. The X-ray powder pattern shows the three most prominent d spacings to be 6.94A, 3.08A, and 2.77A. The results of the differential thermal analysis are given. The deposit in which ezcurrite occurs has been deformed and is predominantly massive recrystallized borax. The borax was probably recrystallized during the deformation and some of it dehydrated under elevated temperatures to form kernite. Ezcurrite, which is less hydrous, was probably also formed at about the same time by crystallizing from solutions released by the dehydration of borax or kernite perviously formed. The temperature necessary to form ezcurrite might or might not have been higher than that for forming kernite. If the temperature was high enough, metakernite might have been formed. Some evidence indicates that the inderite at the deposit is primary. The mineral is named for St. Juan Manuel de Ezcurra, manager of the Cia. Productora de Boratos, S.A., owner of the Tincalayu mine.

Published with the permission of Cia. Productora de Boratos, S.A.

426

EZCURRITE, •1 NEW ,S'ODIUM BOR•ITE 427

INTRODUCTION

EZCURRITE is a new sodium borate mineral from the Tincalayu borax mine in the province of SaRa, Argentina. It is associated with borax (Na=O.2B=- 08.10H,O) and kernitc (Na=O.2B,O•.4H,O), both of which were reported from Tincalayu by Ahlfeld and Angelelli in 1948 (1). Before 1948, kernitc had been reported only from the Kramer district, California (13). Inderite (2MgO.3B,Os. 15H,O) also occurs at Tincalayu; elsewhere it is known to occur only in the Kramer district (7) and in Russia (2). ' Ulexite (Na•-

Solar del

!Salt pan)

Hombre Muerto

•. 4- 4 . 4- 4-

4- 4-

!.:_._-', * 4- 4- 4- +

.i 4- .i-

4-

4-

4- 4- 4-

+ 4- 4- 4- + + 4-

4- .+ 4- + 4- + 4- 4-

:•:.• Alluvium 1• Cenozoic sediments

• Cenozoic volcanic B pyroelastic rocks

• Poleozoic sediments

• Precambrian schists • Precambrian gronitio & gneisslc racks

After Cotaloha (1930)

FIG. 1. Geologic index map of the Tincalayu borax deposit.

O. 2CaO. 5B=O•. 16H20) and secondary tincalconite (Na•O.2B2Os. 5H•O) are also found at Tincalayu.

Tincalayu is on a peninsula that projects southward into the northern part of Salar del Hombre Muerto (Fig. 1). The mine is at an altitude of about 4,000 meters and is 146 km by road south of Pocitos station on the trans- andean General Belgrano railway.

Ezcurrite was originally discovered in 1941 by Messrs. L. D. Osborne and = The inderlte reported by Heinrich (9) from the U.S. is from an unknown locality and

probably came from another country.

428 SIEGFRIED MUESSIG .4ND ROBERT D. ALLEN

H. P. Gower during exploration work at Tincalayu. All specimens were lost, however, and the only record that remained was a chemical analysis in the files of the Compafiia Productora de Boratos, S.A. In 1955 Muessig visited the mine in private interest in the hope that the new mineral could be found again. Unfortunately, the mineral could not be collected in place, but specimens of it were found on the mine dumps.

Although the authors share the responsibility for the contents of this paper, Allen is primarily responsible for the X-ray, DTA, and optical data, and Muessig for the remainder.

Ezcurrite is named for Sr. Juan Manuel de Ezcurra, Manager of the Compafiia Productora de Boratos, S.A., which owns and has recently started to mine the deposit. The writers thank that company for its permission to publish this paper.

GEOLOGY

Regional Setting (Fig. 1).---The borax deposit at Tincalayu occurs within folded and faulted sedimentary rocks that are probably of late Cenozoic age. These rocks crop out in a narrow discontinuous belt that trends roughly north through the island in the central part of Salar del Hombre Muerto and extends northward for many kilometers from the northern shore of the salar. At places about 50 km. north of Tincalayu, rocks of apparently the same age also contain borates (1, 3, 4, 5). To the west and east of the sedimentary belt are north-trending bands of granitic rocks, gneisses, and schists, all of probable Precambrian age, and sedimentary rocks of Paleozoic age. The reader is referred to Catalano's paper (5) for more details of the general geology of the area under discussion, especially with regard to the borate-bearing sediments.

Mine Area (Fig. 2).--The rocks that contain borates are playa sediments of predominantly reddish-colored siltstones, sandstones, and some claystones, that crop out in an anticline whose northern end is bifurcated and faulted. A few thin tuff beds are also present in the section. A thin discontinuous bed of inderite crops out along the sides of the valley and outlines the structure. About 20 m stratigraphically below it lies a series of thin borax beds. Most of the sediments are salty, and red beds that contain much salt crop out promi- nently on the eastern side of the anticlinal structure. On the western side are only a few salt beds, and none on the northern side; their relative absence there is apparently due to abrupt facies changes. Basalt flows unconformably overlie the sediments to the north and west.

Borax Deposit (Fig. 3).--The deposit is a pluglike tabular massive body of predominantly clear and crystalline borax; measured along a northeast line, it is less than 10 m thick and has only a few thin red siltstone and sand- stone layers in it. Underground, little stratification can be seen in the crystalline body, but at the margins the borax content diminishes abruptly and the intercalated and enclosing red sediments dip steeply away from the body in several places. At the end of one of the western drifts on the first level of the mine the edge of the ore body is a fault contact. Borax veins cut the other- wise barren sediments at many places at the margins of the ore body.

The axial plane of the ore body dips very steeply to the northeast nearly

EZCURRITE, .4 NEW SODIUM BOR,4TE 429

Bosolt

•uff

,

""•30

A--a- Inderi• x-x- Borox

Fro. 2.

A B

Sketch map showing the geologic setting of the Tincalayu borax deposit.

at right angles to the eastern branch of the bifurcated anticline. From the attitudes of the sediment outcrops and the discordant relations of the ore body to the enclosing sediments, it seems likely that the ore body is in a faulted block that transects the structure. Moreover, the subsurface structure within the block appears to be tightly anticlinal and may be diapiric.

Mineral Occurrences.--Massive borax is the predominant mineral of the ore body and it has associated with it the new mineral, ezcurrite, and kernite. I(ernite occurs as a few cluster up to about a meter across, completely surrounded by massive borax at a depth of about 20 m below the surface, on the second level of the mine.

430 SIEGFRIED MUESSIG AND ROBERT D. ALLEN

The ezcurrite occurs about 10 m deeper, on the lowest level of the mine. In 1955, this level was not accessible and it was thus not possible to see the mineral in place. The specimens from the mine dumps, however, indicate that the ezcurrite occurs in much the same fashion as the kernite on the level above

it, namely, as clusters of crystalline aggregates surrounded by massive borax. The physical and chemical similarity between ezcurrite and kernite would suggest that they have a similar occurrence. It is not known if kernite occurs with the ezcurrite on the lower level, as the two minerals were not found together in any of the specimens collected on the mine dumps.

Outside the ore body are thin lenticular layers of borax, ulexite and inderite. The borax occurs chiefly as discrete crystals lying in a matrix of reddish and greenish siltstone and shale; the borax in single beds ranges from small to large amounts. Some disseminated borax accompanies the crystal

Fro. 3.

.'?:•-:• .• ..... .3'"'" '•-:;:<- --•¾ • •,•..• '•'•

.: •7• :. • ....• .... .:

ß :

• . •.:... • •--•

View looking northwest at the borax deposit. Men are standing at portal of first level adit.

beds and also occurs alone. The borax crystal layers may be the source bed for the massive borax of the ore body. Interestingly enough, however, the crystal layers are about 20 m stratigraphically below an inderite bed, whereas the top of the massive borax in the ore body is only about 5 m stratigraphically below the same inderite bed.

The inderite referred to above consists of intergrown crystals that are singly terminated and are up to 10 cm across, in a discontinuous bed less than a meter thick (Fig. 4). That the isolated outcrops lie at a single stratigraphic horizon is affirmed by their constant close association with distinctive green siltstones and shales, and tuff beds, and by their uniform stratigraphic distance from other beds that were traced in the field.

EZCURRITE, A NEW SODIUM BORATE 431

Irregular masses of puffy ulexite accompany the inderite in many places. Ulexite also occurs alone as white disseminations and thin irregular beds in the sediments, chiefly below the inderite horizon.

A white powdery crust of tincalconite has formed on borax where this mineral has been exposed to the atmosphere on outcrops, in mine workings, and on the mine dumps. Tincalconite also coats the pieces of kernite on the mine dumps, but this is probably contamination, as the kernite exposed in the mine is unaltered. Menzel and Schulz (12) have shown that on hydration, kernite goes directly to borax without going through the metastable tincalconite phase.

Most of the ezcurrite specimens have a white coating consisting of finely crystalline borax and tincalconite. These minerals are probably contamination from the dumps, which consist chiefly of borax and tincalconite. However,

Fro. 4. Inderite crystals in green clay and shale. White spots are ulexite.

some of the finely crystalline material also occurs along minute cracks and cleavages within the coarsely crystalline ezcurrite and it is likely that it re- sulted from contaminating solutions while exposed on the dumps. A thin section gives no evidence that ezcurrite hydrated to the finely crystalline borax and tincalconite along cleavage cracks.

1• I I•IERALOGY

Ezcurrite occurs as intergrown easily cleavable masses that are moderately striated and have a bladed fibrous structure, some of which is radiating. In- dividual masses are up to 7 cm long and 1.5 cm wide. Two cleavages, one


perfect, and the other less so, intersect at an angle of 71 ø 18.5' (average of 14 goniometer measurements ranging from 71 ø 06' to 71 ø 31'). These cleavages form bent columnar fragments. A poorly developed cleavage meets the zone axis of the other two at a large oblique angie. The cleavages of ezcurrite are much like those of kernite, even as to angle, the two perfect cleavages of kernite, {100} and {001}, meeting at an angle of 71 ø 08'.

Ezcurrite is colorless and transparent and has a vitreous to satiny luster; it looks much like kernite. In hand specimen, ezcurrite can be differentiated

TABLE 1

OPTICAL PROPERTIES OF EZCURRITE AND KERNITE

Ezcurrite Kernitc (Schaller, 13)

aNa 1.472 q- 0.002 1.454 tSNa 1.506 q- 0.002 1.472 qrNa 1.526 q- 0.002 1.488 Birefringence 0.054 q- 0.004 0.034

Biaxial negative (--) Biaxial negative (--)

2V 73• ø (Calc.) 80 ø

Habit Prismatic cleavage fragments, Cleavage fibers micro. untwinned

Orientation q•A elongation: 42.6 ø, the o_Ac: 38• ø average of ten measurements l•Ac: 51• ø ranging from 42.2 ø to 42.9 ø BA elongation: 47.4 ø (by difference)

Elongation

Other

Positive Positive

Fragments with maximum extinction angle between q• and elongation, i.e., 42.6 ø, show acute Nsectrix figures and permit measurement of both/• and Fragments with parallel extinction do not show centered inter- ference figures and permit measurement of a' and 7'. a was measured statistically. The apparent lack of coincidence between optical directions and probable crystallographic axes suggests that ezeurrite is tri- clinic.

Cleavage fibers show parallel extinction. r > v, distinct.

from kernite by its slightly more satiny luster and its more noticeably bent cleavages. Hardness is about 2.5; specific gravity, as measured by suspending clear fragments in a mixture of bromoform and toluene, is 2.153. On heating over a gas flame it clowly swells to an opaque white cauliflowerlike mass, which on further heating fuses to a clear glass. Ezcurrite is very slowly soluble in cold water, slowly soluble in hot water, and easily soluble in acids.

Optical Properties.--The optical properties of ezcurrite and kernitc are summarized in Table 1.

EZCURRITE, A NEW SODIUM BORATE 43,3

TABLE 2

X--RAY DATA FOR EZCU'RRITE AND KERNITE: INTERPLANAR SPACINGS AND RELATIVE INTENSITIES

Cu/Ni; X = 1.5418A; patterns prepared with diffractometer from 20 = 5 ø to 90 ø

Ezcurrite Kernite

d (A) I d (A) I d (A) I d (A)

8.98 1 2.24 <1 7.76 7.69 •1 2.21 •1 7.41 10 2.25 6.94 10 2.14 < 1 6.63 8 2.23 5.50 • 1 2.10 •.1 6.01 1 2.21 5.28 •1 2.09 <1 4.67 4.82 • 1 2.04 • 1 4.30 < 1 2.09 4.48 2 2.02 •1 4.23 4.20 < 1 1.994 • 1 3.90 1 2.05 4.04 • 1 1.955 • 1 3.80 < 1 2.00 3.80 • 1 1.903 • 1 3.70 3 1.957 3.31 2 1.890 < 1 3.51 • 1 1.914 3.22 • 1 1.802 • 1 3.44 •1 1.884 3.19 •1 1.793 •1 3.36 3.13 2 1.734 (1 3.31 3.08 6 1.692 (1 3.25 2 1.746 2.99 <1 1.670 (1 3.13 1 1.722 2.86 • 1 1.642 • 1 2.88 2 1.685 2.77 3 1.590 (1 2.78 2.68 < 1 1.540 < 1 2.68 < 1 1.435 2.64 < 1 1.480 < 1 2.61 1 1.419 2.59 <1 1.459 <1 2.57 <1 1.375 2.53 <1 1.416 <1 2.51 2.45 <1 1.374 <1 2.47 4 2.36 1 1.215 (1 2.39 2.32 <1 1.112 <1 2.34 <1 2.29 <1 2.31

X-ray Data.--X-ray powder patterns of ezcurrite and kernite were prepared with nickel-filtered copper radiation over the range 20 = 5 ø to 90 ø, the spectrum being scanned with a diffractometer at 1 ø per minute with a time constant of 4 seconds. These X-ray patterns are presented in Table 2.

TABLE 3

CHEMICAL ANALYSES OF EZCURRITE AND KERNITE

(In percent)

1 2 3 4

B208 58.86 59.34 58.21 51.02 Na20 20.67 20.37 20.73 22.66 H•O (20.47) 20.89 21.06 26.32

100.00 100.60 100.00 100.00

1. Ezcurrite, water by difference. Ralph Mathieson, analyst. Qualitative tests for NHs, P20•, SO4, C1, F, and CO• were negative: Hy Almond, analyst.

2. Ezcurrite. Henry Kramer, analyst. 3. 2Na•O .SB•O,. 7H•O, theoretical ezcurrite. 4. Na=O. 2B20,-4H•0, theoretical kernire.


CHEMICAL ANALYSES

Chemically, ezcurrite is much like kernite, but it has slightly less water of crystallization and its constituents have different combining ratios. Chemical analyses of these two minerals are presented in Table 3.

According to the analysis (Table 3, no. 1) of ezcurrite, the molecular ratios are: Na20•0.3334; B20•0.8452; H•O--1.1360; or: Na•.O--1.000; B•O8-- 2.536; H•O--3.408.

A spectrographic analysis made by Hal W. Johnson, Pacific Spectro- chemical Laboratory, Los Angeles, California, is tabulated below, in percent.

XO.O B, Na X.O not reported O.X not reported O.OX Si, A1 O.OOX Ag, Fe, Ca, Cu O.OOOX Mg

DEGREES CENTIGRADE

I00 200 SO0

EZCURRITE ARGENTINA

EZCURRITE

ARGENTINA

KERNITE KRAMER DISTRICT

CALIF.

FIc. 5. Differential thermal analyses curves of ezcurrite and kernite. Heating rate: 30 ø C per minute; medium sensitivity.

EZCURRITE, .4 NEIIz SODIUM BOR.4TE 435

DIFFERENTIAL THERMAL ANALYSES

Two differential thermal analysis curves of ezcurrite were prepared from data obtained using a portable differential thermal analysis unit, manufactured by the Eberbach Corporation. An earlier model of this portable unit was described by Hendricks, Goldich, and Nelson (10). The mineral was sieved to minus 50 plus 200 mesh and heated at a rate of 30 ø C per minute, starting with a cold furnace. This heating rate was maintained with the following voltage settings of a variable transformer: 50-200 ø C, 82 volts; 200-300 ø C, 85 volts; 300-350 ø C, 90 volts. The medium sensitivity adjustment gave satisfactory instrumental response. The ezcurrite curves, and for comparison, a curve of kernite from the Kramer district, California, are given in Figure 5.

The principal data supplied by these curves are summarized as follows:

Ezcurrite Kernite

Initial Endothermic temperature of trough

endothermic temperature reaction (øC) (øC)

160 to 170 260 to 265 100 185

DISCUSSION

Ezcurrite and the two accompany/ng borates, kernire and borax, as viewed in the light of their different waters of crystallization and their occurrence in different geologic environments, shed considerable light on the genesis of the Tincalayu borate deposit. This genesis, as outlined below, is consistent with both the field and laboratory data, and also with the genesis of the other known like deposit, that at Kramer, California.

Borax was deposited. as crystals in a salar, or salt pan, together with red clastic sediments and some salt, a process that seems to be still going on today in several s•ares in Argentina. The borax in beds outside the ore body (Fig. 2), which are only slightly deformed and contain no kernire or ezcurrite, still occurs in the form of the primary crystals. The borax was buried under other sediments, which included borax and ulexite, and probably also inderite, which may be a primary mineral at this place.

After burial, the sediments were folded and faulted. At the ore body--in which kernire and ezcurrite occur•eformation was more intense than else-

where and the original borax was probably pushed upward into a pluglike mass and was recrystallized from discrete crystals to a massive form. As the deposit has not been bottomed, the source bed of the massive borax is not certainly known.

Some of the borax alehydrated to form kernire, which is a higher temperature mineral (13, 12). Ezcurrite, which is the least hydrous of the three sodium borates discussed here and retains its water of crystallization to higher temperatures than the other two borates, probably also formed at about the same time by crystallizing from solutions released by the dehydration of borax or of kernire previously formed. In solution, the stable transition point of borax to kernire is $8.2 ø C at atmospheric pressure (12).

436 SIEGFRIED MUESSIG •IND ROBERT D. ALLEN

The temperature necessary to form ezcurrite might have been higher or lower than that for forming kernire. But temperature was probably not the only variable factor that determined which of the sodium borates formed; the relative amounts of Na20, B•03, and I-I20 available at the place and time of new-mineral crystallization might finally have determined which of the minerals formed: recrystallized borax, kernite, or ezcurrite.

Experiments in the system Na•O-B•O3-I-I•O have not produced ezcurrite to date, and hence its temperature of formation at atmospheric pressure is not known. Until it is known, nothing can be said regarding the highest temperatures reached at the ore body during deformation. Further, when this is known, it might be possible to speculate whether the synthetic metakernite (Na•O.2B•Oa. 2I-I•O(11)) should have formed and should be looked for at Tincalayu.

The structural setting of the ore body indicates that higher pressures, and therefore higher temperatures at constant volume, probably existed only here during deformation. That recrystallized borax, and the less hydrous forms, kernite and ezcurrite, occur nowhere else in the area is consistent with the above inference.

In many respects, the Tincalayu deposit is like the sodium borate deposit at Kramer, California. At Kramer, kernire is associated with primary borax and both Schaller (13) and Gale (8) regard its presence as evidence of elevated temperatures. There also, the kernite is associated with much recrystallized massive borax, whereas in areas where kernire does not occur, the borax is predominantly in the form of euhedral crystal layers. Inderite is now also known at Kramer (7), but its occurrence is different from that at Tincalayu and may or may not have bearing on the genesis of the deposits as viewed from a standpoint of their mineralogical similarity. Ezcurrite has not been found at Kramer, but it might well occur, especially in the deeper parts of the deposit.

The Tincalayu deposit differs further from that at Kramer in being more deformed, and in not having the associated arsenic and antimony minerals, nor the calcium, and sodium-calcium borates, colemanire and probertite. More- over, the salty sediments, such as occur at Tincalayu, are strikingly absent at Kramer. (Did NaC1 play a role in the formation of ezcurrite at Tincalayu?)

There is no conclusive evidence that the inderite at Tincalayu is primary, and it has not been found forming under surface conditions anywhere in the world. Some lines of evidence, however, suggest that the inderite is primary: 1. It occurs chiefly as aggregates of well-formed singly terminated crystals at one stratigraphic horizon. 2. Inderite was not found as pseudomorphs after other borate minerals, or as veins, or with crystallographic orientations com- mon to anything but single inderite crystals. 3. The mineral is apparently a low-temperature form; its synthesis at 35 ø C (6) and its high content of water of crystallization bear this out.

Ezcurrite differs from minerals of the borax-kernite series (NagO.2B•- Oa.nI-I•O) in having a different molecular NagO-B•Oa ratio: 2: 5. It is

EZCURRITE, A NEW SODIUM BORATE 437

perhaps but one mineral of a new sodium borate series (2Na20.5B•Oa. nH•O) that might exist in nature.

U.S. GEOLOGICAL SURVEY, So. 157 HOWARD ST.,

SPOKANE 4, WASHINGTON AND

J•r PROPULSION LAB., 4800 OAK GROVE DroVE,

PASADENA, CALIFORNIA, October 25, 1956

REFERENCES

1. Ahlfeld, Federico, and Angelelli, Victorio, 1948, Las especies minerales de la RepubIica Argentina: Univ. Nac. de Tucuman, Inst. de Geol. y Mineria, (Jujuy), Pub. 458, p. 162-168.

2. Boldyreva (1937) in Palache, C., Betman, H., and Frondel, C., 1951, The System of Mineralogy: John Wiley and Sons, New York, 7th ed., v. 2, p. 360.

3. Catalano, Luciano R., 1926, Geologla econ6mica de los yacimientos de boratos y materiales de las euencas, Salar Cauchari: Ministerio de Agr. de la Naci6n, Dir. Gen de Minas, Geol. e Hidrologla, no. 23, p. 49-54.

4. , 1927, Geologia qulmica de los boratos; formaci6n de las euencas y caracteristieas generales de la superfieie de los salares, Puna de Atacama, Republiea Argentina: Ministe- rio de Agr. de la Naei6n, Dir. Gem de Minas, Geol. e Hidrologia, no. 28, 101 p.

5. •, 1930, Puna de Ataeama; Resefta geo16gica y geogr•tfica: Univ. Nae. del Litoral, Pub. 8 del Depto. de extensi6n universitaria, 106 p.

6. Feigelson, Grushvitsky, and Korobochkina (1939); Nikolaev and Chelishcheva (1940) in Palache, C., Berman, H., and Frondel, C., 1951, The System of Mineralogy: John Wiley and Sons, New York, 7th ed., v. 2, p. 361.

7. Frondel, Clifford, and Morgan, Vincent, 1956, Inderite and gerstleyite from the Kramer borate district, Kern County, California: Am. Mineralogist, v. 41, p. 839-843.

8. Gale, Hoyt S., 1946, Geology of the Kramer borate district, Kern County, California: Calif. Jour. Mines and Geol., State Mineral. Rept., v. 42, no. 4, p. 325-378.

9. Heinrich, Eberhardt W., 1946, A second discovery of inderite (from California): Am. Mineralogist, v. 31, nos. 1-2, p. 71-76.

10. Hendricks, S. B., Goldieh, S.S., and Nelson, R. A., 1946, A portable differential thermal analysis unit for bauxite exploration: Ecom G•.o•.., v. 41, p. 64-76.

11. Henzel, H., Schulz, H., Sieg, L., Voigt, M., 1935, Zur Kenntnis der Bors/iuren und borsauren Alkalisalze. IX. Das System Na•B•O,.H•O: Z. anorg. allg. Chem., Bd. 224, p. 1-22. .

12. •., and Schulz, H., 1940, Zur Kenntnis der Bors/iuren und borsauren Alkalisalze. X. Der Kernit (Rasorit) Na=B•O•.4H=O: Z. anorg. allg. Chem., Bd. 245, p. 157-220.

13. Schaller, Waldemar T., 1930, Borate minerals from the Kramer district, Mobave Desert, California: U.S. Geol. Survey Prof. Paper 158-1, p. 137-170.

Documents

Muessig and Allen-1957