BOWENS REACTION SERIES Within the field of geology, Bowen's reaction series is the work of the petrologist, Norman L. Bowen who was able to explain why certain types of minerals tend to be found together while others are almost never associated with one another. He experimented in the early 1900s with powdered rock material that was heated until it melted and then allowed to cool to a target temperature whereupon he observed the types of minerals that formed in the rocks produced. He repeated this process with progressively cooler temperatures and the results he obtained led him to formulate his reaction series which is still accepted today as the idealized progression of minerals produced by cooling magma. Based upon Bowen's work, one can infer from the minerals present in a rock the relative conditions under which the material had formed. [edit]Description The series is broken into two branches, the continuous and the discontinuous. The branch on the right is the continuous. The minerals at the top of the illustration (given aside) are first to crystallize and so the temperature gradient can be read to be from high to low with the high temperature minerals being on the top and the low temperature ones on the bottom. Since the surface of the Earth is a low temperature environment compared to the zones of rock formation, the chart also easily shows the stability of minerals with the ones at bottom being most stable and the ones at top being quickest to weather, known as theGoldich dissolution series. This is because minerals are most stable in the conditions closest to those under which they had formed. Put simply, the high temperature minerals, the first ones to crystallize in a mass of magma, are most unstable at the Earth's surface and quickest to weather because the surface is most different from the conditions under which they were created. On the other hand, the low temperature minerals are much more stable because the conditions at the surface are much more similar to the conditions under which they formed.

ALBITE

Albite is a felsic plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. As such it represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula NaAlSi3O8. It is a tectosilicate. Its color is usually pure white, hence its name from Latin albus.

Albite

Albite crystallizes with triclinic pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 - 6.5. Albite almost always exhibits crystal twinning often as minute parallel striations on the crystal face. Albite often occurs as fine parallel segregations alternating with pink microcline inperthite as a result of exolution on cooling. It occurs in granitic and pegmatite masses, in some hydrothermal vein deposits and forms part of the typical greenschist metamorphic facies for rocks of originally basaltic composition. It was first reported in 1815 for an occurrence in Finnbo, Falun, Dalarna, Sweden.[2]

Albite

Albite from Crete, scale = 1 in.

General

Category

plagioclase, feldspar,tectosilicate

Formula(repeating unit)

NaAlSi3O8 or Na1.00.9Ca0.00.1Al1.01.1Si3.02.9O8

Crystal symmetry

Triclinic HM Symbol 1

Unit cell

a = 8.16 , b = 12.87 , c = 7.11 ; = 93.45, = 116.4, = 90.28; Z=4

Identification

Color

White to gray, blueish, greenish, reddish; may bechatoyant

Crystal habit

Crystals commonly tabular, divergent aggregates, granular, cleavable massive

Crystal system

Triclinic Pinacoidal

Twinning

Coomon giving polysynthetic striae on {001} or {010}also contact, simple and multiple

Cleavage

Perfect on {001}, very good on {010}, imperfect on {110}

Fracture

Uneven to conchoidal

Tenacity

Brittle

Mohs scalehardness

6 6.5

Luster

Vitreous, typically pearly on cleavages

Streak

White

Diaphaneity

Transparent to translucent

Specific gravity

2.60 - 2.65

Optical properties

Biaxial (+)

Refractive index n = 1.528 1.533 n = 1.532 1.537 n = 1.538 1.542

Birefringence

= 0.010

2V angle

8590 (low); 5254 (high)

Dispersion

r < v weak

Other

Low- and high-temperature structural

characteristics

modifications are recognized

ALMANDINE (GARNET)

Almandine (pron.: /lmndn/), also known incorrectly as almandite, is a species of mineral belonging to the garnet group. The name is a corruption of alabandicus, which is the name applied by Pliny the Elder to a stone found or worked at Alabanda, a town in Caria in Asia Minor. Almandine is an iron alumina garnet, of deep red color, inclining to purple. It is frequently cut with a convex face, or en cabochon, and is then known as carbuncle. Viewed through the spectroscope in a strong light, it generally shows three characteristic absorption bands. Almandine is one end-member of a mineral solid solution series, with the other end member being the garnet pyrope. The almandine crystal formula is: Fe3Al2(SiO4)3. Magnesium substitutes for the iron with increasingly pyrope-rich composition. Almandine, Fe 3Al2Si3O12, is the ferrous iron end member of the class of garnet minerals representing an important group of rock-formingsilicates, which are the main constituents of the Earth's crust, upper mantle and transition zone. Almandine crystallizes in the cubic space group Ia3d, with unit-cell parameter [2] a 11.512 at 100 K. Almandine is antiferromagnet with the Nel temperature of 7.5 K. It contains two equivalent magnetic [3] sublattices. [edit]Occurrence2+

Almandine

Almandine occurs rather abundantly in the gem-gravels of Sri Lanka, whence it has sometimes been called Ceylon-ruby. When the color inclines to a violet tint, the stone is often called Syriam garnet, a name said to be taken from Syriam, an ancient town of Pegu (now part ofMyanmar). Large deposits of fine almandine-garnets were found, some years ago, in theNorthern Territory of Australia, and were at first taken for rubies and thus they were known in trade for some time afterwards as Australian rubies. Almandine is widely distributed. Fine rhombic dodecahedra occur in the schistose rocks of theZillertal, in Tyrol, and are sometimes cut and polished. An almandine in which the ferrous oxide is replaced partly by magnesia is found at Luisenfeld in German East Africa. In the United States there are many localities which yield almandine. Fine crystals of almandine embedded in mica-schist occur near Wrangell in Alaska. The coarse varieties of almandine are often crushed for use as an abrasive agent.

Almandine

General

Category

Nesosilicate

Formula(repeating unit)

Fe2+3Al2Si3O12

Strunz classification

09.AD.25

Identification

Color

reddish orange to red, slightly purplish red to reddish purple and usually dark in tone

Cleavage

none

Fracture

conchoidal [1]

Mohs scalehardness

7 - 7.5

Luster

greasy to vitreous

Specific gravity

4.05 (+.25, -.12) [1]

Polish luster

vitreous to subadamantine [1]

Optical properties

Single refractive, and often anomalous double refractive [1]

Refractive index

1.790 (+/- .030) [1]

Birefringence

none

Pleochroism

none

Dispersion

.024 [1]

Ultravioletfluorescence inert

Absorption spectra

usually at 504, 520, and 573nm, may also have faint lines at 423, 460, 610 and 680-690nm [1]

AMAZONITE (MICROCLINE) Amazonite (sometimes called "Amazon stone") is a green variety of microcline feldspar.[1]

The name is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon area. Amazonite is a mineral of limited occurrence. Formerly it was obtained almost exclusively from the area of Miass in the Ilmen mountains, 50 miles southwest of Chelyabinsk, Russia, where it occurs in granitic rocks. More recently, high-quality crystals have been obtained from Pike's Peak, Colorado, where it is found associated with smoky quartz, orthoclase, and albite in a coarse granite or pegmatite. Crystals of amazonite can also be found in Crystal Park, El Paso County, Colorado. Other localities in the United [2] States which yield amazonite include the Morefield Mine in Amelia, Virginia. It is also found in pegmatite inMadagascar and in Brazil. Because of its bright green color when polished, amazonite is sometimes cut and used as a gemstone, although it is easily fractured. For many years, the source of amazonite's color was a mystery. Naturally, many people assumed the color was due to copper because copper compounds often have blue and green colors. More recent [3] studies suggest that the blue-green color results from small quantities of lead and water in the feldspar.

Microcline (KAlSi3O8) is an important igneous rock-forming tectosilicate mineral. It is a potassiumrich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling oforthoclase; it is more stable at lower temperatures than orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature. Microcline may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by crosshatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline. Microcline may be chemically the same as monoclinic orthoclase, but because it belongs to the triclinic crystal system, the prism angle is slightly less than right angles; hence the name "microcline" from the Greek "small slope." It is a fully ordered triclinicmodification of potassium feldspar and is dimorphous with orthoclase. Microcline is identical to orthoclase in many physical properties; it can be distinguished by x-ray or optical examination; viewed under a polarizing microscope, microcline exhibits a minute multipletwinning which forms a grating-like structure that is unmistakable.

Feldspar (Amazonite)

Perthite is either microcline or orthoclase with thin lamellae of exsolved albite. Amazon stone, or amazonite, is a beautiful green variety of microcline. It is not found anywhere in the Amazon basin, however. Spanish explorers who named it apparently confused it with another green mineral from that region. The largest documented single crystals of microcline were found in Devils Hole Beryl Mine,Colorado, US [1] and measured ~50x36x14 m. This could be one of the largest crystals of any material found so far.

APATITE

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, named for high concentrations of OH ,F , Cl or ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca10(PO4)6(OH,F,Cl)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6(F)2 and Ca10(PO4)6(Cl)2. Apatite is one of a few minerals produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material. Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite; in the mid-20th century, it was discovered that communities whose water supply naturally contained fluorine had lower [3] rates of dental caries. Fluoridated water allows exchange in the teeth of fluoride ions forhydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions (e.g. sodium

fluoride, sodium monofluorophosphate). Too much fluoride results in dental fluorosis and/or skeletal fluorosis. Fission tracks in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basins.(U-Th)/He dating of apatite is also well established for use in determining thermal histories and other, less typical applications such as paleo-wildfire dating. Phosphorite is a phosphate-rich sedimentary rock, that contains between 18% and 40% P2O5. The apatite in phosphorite is present ascryptocrystalline masses referred to as collophane.

Apatite

General

Category

Phosphate mineral group

Formula(repeating unit)

Ca5(PO4)3(F,Cl,OH)

Strunz classification

08.BN.05

Identification

Color

Transparent to translucent, usually green, less often colorless, yellow, blue to violet, pink, brown.[1]

Crystal habit

Tabular, prismatic crystals, massive, compact or granular

Crystal system

Hexagonal dipyramidal (6/m)[2]

Cleavage

[0001] indistinct, [1010] indistinct[2]

Fracture

Conchoidal to uneven[1]

Mohs scalehardness

5[1] (defining mineral)

Luster

Vitreous[1] to subresinous

Streak

White

Diaphaneity

Transparent to translucent[2]

Specific gravity

3.163.22[2]

Polish luster

Vitreous[1]

Optical properties

Double refractive, uniaxial negative[1]

Refractive index

1.6341.638 (+0.012, 0.006)[1]

Birefringence

0.0020.008[1]

Pleochroism

Blue stones strong, blue and yellow to colorless. Other colors are weak to very weak.[1]

Dispersion

0.013[1]

Ultravioletfluorescence Yellow stones purplish pink which is stronger in long wave;blue stones blue to light blue in both long and short wave; green stones greenish yellow

which is stronger in long wave; violet stones greenish yellow in long wave, light purple in short wave.[1]

ARAGONITE

Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3 (the other form being themineral calcite). It is formed by biological and physical processes, including precipitation from marine and freshwater environments. Aragonite's crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic system with acicular crystals. Repeatedtwinning results in pseudo-hexagonal forms. Aragonite may be columnar or fibrous, occasionally in branching stalactitic forms called flos-ferri("flowers of iron") from their association with the ores at the Carinthian iron mines.

OccurrenceThe type location for aragonite is Molina de Aragn (Guadalajara, Spain), 25 km from Aragon for which it [1] was named in 1797. An aragonite cave, the Ochtinsk Aragonite Cave, is situated in Slovakia. In the USA, aragonite in the form of stalactites and "cave flowers" (anthodite) is known fromCarlsbad Caverns and other caves. Massive deposits of oolitic aragonite sand are found on the seabed in the Bahamas. Aragonite forms naturally in almost all mollusk shells, and as the calcareous endoskeleton of warm- and cold-water corals (Scleractinia). Severalserpulids have aragonitic tubes. Because the mineral deposition in mollusk shells is strongly biologically controlled, some crystal forms are distinctively different from those of inorganic aragonite. In some mollusks, the entire shell is aragonite; in others, aragonite forms only discrete parts of a bimineralic shell (aragonite plus calcite). Aragonite also forms in the ocean and in caves as inorganic precipitates called marine cements andspeleothems, respectively. The nacreous layer of the aragonite fossil shells of some extinct ammonites forms an iridescent material called ammolite. Ammolite is primarily aragonite with impurities that make it iridescent and valuable as a gemstone. Aragonite is metastable and is thus commonly replaced by calcite in fossils. Aragonite older than [4] the Carboniferous is essentially unknown. [edit]Physical

properties

Aragonite is thermodynamically unstable at standard temperature and pressure, and tends to alter 7 8 to calcite on scales of 10 to 10 years. The mineral vaterite, also known as -CaCO3, is another phase of calcium carbonate that is metastable at ambient conditions typical of Earth's surface, and decomposes even more readily than aragonite. [edit]Uses In aquaria, aragonite is considered essential for the replication of reef conditions in aquariums. needed] It not only is the material that the sea life is evolved to use and live around, but also keeps the tank's pH close to its natural level.[citation

Aragonite

Aragonite from Salsignes Mine, Aude department, France Size: 30x30x20 cm

General

Category

Carbonate mineral

Formula(repeating unit)

CaCO3

Strunz classification

05.AB.15

Crystal symmetry

Orthorhombic (2/m 2/m 2/m) - dipyramidal

Unit cell

a = 4.95 , b = 7.96 , c = 5.74 ; Z = 4

Identification

Color

White, red, yellow, orange, green , blue and brown

Crystal habit

Pseudohexagonal, prismatic crystals, acicular, columnar, globular, reniform, pisolitic, coralloidal, stalactitic, internally banded

Crystal system

Orthorhombic

Twinning

Polysynthetic parallel to {100} cyclically on {110}

Cleavage

Distinct on {010}, imperfect {110} and {011}

Fracture

Subconchoidal

Tenacity

Brittle

Mohs scalehardness

3.5-4

Luster

Vitreous, resinous on fracture surfaces

Streak

White

Diaphaneity

Translucent to transparent

Specific gravity

2.95

Optical properties

Biaxial (-)

Refractive index

n = 1.529 - 1.530 n = 1.680 - 1.682 n = 1.685 - 1.686

Birefringence

= 0.156

2V angle

18

Solubility

Dilute acid

Other

Fluorescence: pale rose, yellow, white or

characteristics

bluish; phosphorescence: greenish or white (LW UV); yellowish (SW UV)

AUGITE

Augite is a common rock forming single chain inosilicate mineral with formula (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6. The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. [edit]Characteristics

Euhedral crystal of augite fromTeide (4.4 x 3.0 x 2.3 cm)

Augite is a solid solution in the pyroxene group. Diopside and hedenbergite are important endmembers in augite, but augite can also contain significant aluminium, titanium, and sodium and other elements. The calcium content of augite is limited by a miscibility gap between it and pigeonite and orthopyroxene: when occurring with either of these other pyroxenes, the calcium content of augite is a function of temperature and pressure, but mostly of temperature, and so can be useful in reconstructing temperature histories of rocks. With declining temperature, augite may exsolve lamellae of pigeonite and/or orthopyroxene. There is also a miscibility gap between augite andomphacite, but this gap occurs at lower temperature and is not well understood. [edit]Locations It's an essential mineral in mafic igneous rocks; for example, gabbro and basalt and common in ultramafic rocks. It also occurs in relatively high-temperature metamorphic rocks such as mafic granulite and metamorphosed iron formations. It commonly occurs in association [1] with orthoclase, sanidine, labradorite, olivine, leucite, amphibolesand other pyroxenes. Occasional specimens have a shiny appearance that give rise to the mineral's name, which is from the Greekaugites, meaning "brightness", although ordinary specimens have a dull (dark green, brown or [2] black) luster. It was named by Abraham Gottlob Werner in 1792. Transparent augites containing dendritic patterns are used as gems and ornamental stones known [4] as shajar in parts of India. It is found near the Ken River. Local jewelers export raw shajar stone and [5] items to different parts of India. Banda is one city noted for trade of shazar stone.

Augite

Augite - Muhavura volcano

General

Category

Silicate mineral

Formula(repeating unit)

(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6

Strunz classification

9.DA.15

Crystal symmetry

Monoclinic prismatic H-M symbol: (2/m) Space group: C 2/c

Unit cell

a = 9.699 , b = 8.844 , c = 5.272 ; = 106.97; Z=4

Identification

Color

Black, brown, greenish, violet-brown; in thin section, colorless to gray with zoning common

Crystal habit

Commonly as stubby prismatic crystals, also acicular, skeletal, dendritic

Crystal system

Monoclinic

Twinning

Simple or multiple on {100} and {001}

Cleavage

{110} good with 87 between {110} and {110}; parting on {100} and {010}

Fracture

uneven to conchoidal

Tenacity

brittle

Mohs scalehardness

5.5 to 6

Luster

Vitreous, resinous to dull

Streak

Greenish-white

Diaphaneity

Transparent to opaque

Specific gravity 3.19 - 3.56

Optical properties

Biaxial (+)

Refractive index

n = 1.680 - 1.735, n = 1.684 - 1.741, n = 1.706 - 1.774

Birefringence

= 0.026 - 0.039

Pleochroism

X = pale green, pale brown, green, greenish yellow; Y = pale brown, pale yellow-green, violet; Z = pale green, grayish green, violet

AZURITE Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also [2] known as Chessylite after the type locality atChessy-les-Mines near Lyon, France. The mineral, a carbonate, has been known since ancient times, and was mentioned in Pliny the Elder'sNatural History under the Greek name kuanos (: "deep blue," root of English cyan) and the Latin [4] name caeruleum. The blue of azurite is exceptionally deep and clear, and for that reason the mineral has tended to be associated since antiquity with the deep blue color of low-humidity desert and winter skies. The modern English name of the mineral reflects this association, since both azurite and azure are derived via Arabic from the Persian lazhward (), an area known for its deposits of another deep blue stone, lapis lazuli ("stone of azure"). [edit]Mineralogy

Fresh, unweathered stalactitic azurite crystals showing the deep blue of unaltered azurite

Malachite pseudomorf after azurite. With azurite, and unknown white crystals. From Tsumeb, Namibia.

Ground azurite powder for use as a pigment.

Azurite deposits on the interior surface of a geode

Azurite is one of the two basic copper(II) carbonate minerals, the other being bright green malachite. Simple copper carbonate (CuCO3) is not known to exist in nature. Azurite has the formula Cu3(CO3)2(OH)2, with the copper(II) cations linked to two different anions, carbonate and hydroxide. Small crystals of azurite can be produced by rapidly stirring a few drops of copper sulfate solution into asaturated solution of sodium carbonate and allowing the solution to stand overnight. Azurite crystals are monoclinic, and when large enough to be seen they appear as dark blue prismatic [2][3][5] crystals. Azurite specimens are typically massive to nodular, and are often stalactitic in form. Specimens tend to lighten in color over time due to weathering of the specimen surface into malachite. Azurite is soft, with a Mohs hardness of only 3.5 to 4. The specific gravity of azurite is 3.77 to 3.89. Azurite is destroyed by heat, losing carbon dioxide and water to form black, powdery copper(II) oxide. Characteristic of a carbonate, specimens effervesce upon treatment with hydrochloric acid.

[edit]Color The optical properties (color, intensity) of minerals such as azurite and malachite are explained in the context of conventional electronic spectroscopy of coordination complexes. Relatively detailed descriptions are provided by ligand field theory. [edit]Weathering Azurite is unstable in open air with respect to malachite, and often is pseudomorphically replaced bymalachite. This weathering process involves the replacement of some the carbon dioxide (CO 2) units with water (H2O), changing the carbonate:hydroxide ratio of azurite from 1:1 to the 1:2 ratio of malachite: 2 Cu3(CO3)2(OH)2 + H2O 3 Cu2(CO3)(OH)2 + CO2 From the above equation, the conversion of azurite into malachite is attributable to the low partial pressure of carbon dioxide in air. Azurite is also incompatible with aquatic media, such as saltwater aquariums. [edit]Uses [edit]Pigments Azurite was used as a blue pigment for centuries. Depending on the degree of fineness to which it was ground, and its basic content of copper carbonate, it gave a wide range of blues. It has been known asmountain blue or Armenian stone, in addition it was formerly known as Azurro Della Magna (from Italian). When mixed with oil it turns slightly green. When mixed with egg yolk it turns greengrey. It is also known by the names Blue Bice and Blue Verditer, though Verditer usually refers to a pigment made by chemical process. Older examples of azurite pigment may show a more greenish tint due to weathering into malachite. Much azurite was mislabeled lapis lazuli, a term applied to many blue pigments. As chemical analysis of paintings from the Middle Ages improves, azurite is being recognized as a major source of the blues used by medieval painters. True lapis lazuli was chiefly supplied from Afghanistan during the Middle Ages while azurite was a common mineral in Europe at the time. Sizable deposits were found near Lyons, France. It was mined since the 12th [6] century in Saxony, in the silver mines located there. Heating can be used to distinguish azurite from purified natural ultramarine blue, a similar but much more expensive pigment, as described by Cennino D'Andrea Cennini. Ultramarine withstands heat, but azurite turns to black copper oxide. However, gentle heating of azurite produces a deep blue pigment used in Japanese painting techniques. [edit]Jewelry Azurite is used occasionally as beads and as jewelry, and also as an ornamental stone. However, its softness and tendency to lose its deep blue color as it weathers limit such uses. Heating destroys azurite easily, so all mounting of azurite specimens must be done at room temperature. [edit]Collecting[show]Left frame [hide]Right frame

[show]Parallel view ( ) [show]Cross-eye view ( )

Small specimen of Azurite from China.

The intense color of azurite makes it a popular collector's stone. However, bright light, heat, and open air all tend to reduce the intensity of its color over time. To help preserve the deep blue color of a pristine azurite specimen, collectors should use a cool, dark, sealed storage environment similar to that of its original natural setting. [edit]Prospecting While not a major ore of copper itself, the presence of azurite is a good surface indicator of the presence of weathered copper sulfide ores. It is usually found in association with the chemically very similar malachite, producing a striking color combination of deep blue and bright green that is strongly indicative of the presence of copper ores.

Azurite

Azurite from China with large crystals and light surface weathering.

General

Category

Carbonate mineral

Formula(repeating unit)

Cu3(CO3)2(OH)2

Strunz classification

05.BA.05

Crystal symmetry

Monoclinic 2/m

Unit cell

a = 5.01 , b = 5.85 , c = 10.35 ; = 92.43; Z=2

Identification

Formula mass

344.67 g/mol

Color

Azure-blue, Berlin blue, very dark to pale blue; pale blue in transmitted light

Crystal habit

Massive, prismatic, stalactitic, tabular

Crystal system

Monoclinic Prismatic

Twinning

Rare, twin planes {101}, {102} or {001}

Cleavage

Perfect on {011}, fair on {100}, poor on {110}

Fracture

Conchoidal

Tenacity

brittle

Mohs scalehardness

3.5 to 4

Luster

Vitreous

Streak

Light Blue

Diaphaneity

Transparent to translucent

Specific gravity

3.773 (measured), 3.78 (calculated)

Optical properties

Biaxial (+)

Refractive index

n = 1.730 n = 1.758 n = 1.838

Birefringence

= 0.108

Pleochroism

Visible shades of blue

2V angle

Measured: 68, calculated: 64

Dispersion

relatively weak

BAUXITE

Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al(OH)3, boehmite -AlO(OH), and diaspore -AlO(OH), in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anataseTiO2. Bauxite was named after the village Les Baux in southern France, where it was first recognised as containing aluminium and named by the French geologist Pierre Berthier in 1821. [edit]Bauxite

formation

Lateritic bauxites (silicate bauxites) are distinguished from karst bauxite ores (carbonate bauxites). The early discovered carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of intercalated clays or by clay dissolution residues of the limestone. The lateritic bauxites are found mostly in the countries of the tropics. They were formed by lateritization of various silicate rocks such as granite, gneiss,basalt, syenite, and shale. In comparison with the iron-rich laterites, the formation of bauxites demands even more on intense weathering conditions in a location with very good drainage. This enables the dissolution of the kaolinite and the precipitation of the gibbsite. Zones with highest aluminium content are frequently located below a ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite. In the case of Jamaica, recent analysis of the soils showed elevated levels of cadmium suggesting that the bauxite originates from recent Miocene ashdeposits from episodes of significant volcanism in Central America.

[edit]Production

trends

In 2010, Australia was the top producer of bauxite with almost one-third of the world's production, followed by China, Brazil, India, and Guinea. Although aluminium demand is rapidly increasing, known reserves of its bauxite ore are sufficient to meet the worldwide demands for aluminium for many [citation needed] centuries. Increased aluminium recycling, which has the advantage of lowering the cost in electric power in producing aluminium, will considerably extend the world's bauxite reserves.

BARITE

Baryte, or barite, (BaSO4) is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main [1] source of barium. Baryte and celestine form a solid solution (Ba,Sr)SO4. [edit]Names

[2]

and history

The unit cell of barite

The radiating form, sometimes referred to as Bologna Stone, attained some notoriety among alchemistsfor the phosphorescent specimens found in the 17th century near Bologna by Vincenzo [6] Casciarolo. The American Petroleum Institute specification API 13/ISO 13500 which governs baryte for drilling purposes does not refer to any specific mineral, but rather a material that meets that specification. In practice this is usually the mineral baryte. The term "primary baryte" refers to the first marketable product, which includes crude baryte (run of mine) and the products of simple beneficiation methods, such as washing, jigging, heavy media separation, tabling, flotation. Most crude baryte requires some upgrading to minimum purity or density. Baryte that is used as an aggregate in a "heavy" cement is crushed and screened to a uniform size. Most baryte is ground to a small, uniform size before it is used as a filler or extender, an addition to industrial products, or a weighting agent in petroleum well drilling mud. [edit]Name The name baryte is derived from the Greek word (heavy). The American [2][7] spelling is barite. The International Mineralogical Associationadopted "barite" as the official spelling [citation needed] when it formed in 1959 , but recommended adopting the older "baryte" spelling in [8] 1978, notably ignored by the Mineralogical Society of America. Other names have been used for baryte, including barytine, [2] [3] Spar, tiff, and blanc fixe. [edit]Mineral[8]

barytite,

[8]

schwerspath,

[8]

barytes,

[2]

Heavy

associations and locations

Baryte with Galena and Hematite from Poland

Large barite crystals from Nevada, USA

Abandoned baryte mine shaft near Aberfeldy, Perthshire, Scotland.

Baryte occurs in a large number of depositional environments, and is deposited through a large number [1] of processes including biogenic, hydrothermal, and evaporation, among others. Baryte commonly occurs in lead-zinc veins in limestones, in hot spring deposits, and with hematite ore. It is often [9] associated with the minerals anglesite and celestine. It has also been identified in meteorites.

Baryte has been found at locations in Brazil, Canada, Chile, China, India, Greece, Iran, Ireland (where it [10] was mined on Benbulben ), Liberia, Morocco, Peru, Romania (Baia Sprie), Turkey, South [11] Africa(Barberton Mountain Land), Thailand, UK (Cornwall, Cumbria, Derbyshire, Durham, Muirshiel [2] Mine,Perthshire, Argyllshire & Surrey ) and USA (Cheshire, Connecticut, De Kalb, New York & Fort Wallace, New Mexico. It is mined in Arkansas, Connecticut, Virginia, North [2] Carolina, Georgia, Tennessee,Kentucky, Nevada & Missouri. ) The major baryte producers (in thousand tonnes, data for 2010) are as follows: China (3,600), India [12] (1,000), United States (670), Morocco (460), Iran (250), Turkey (150) and Kazakhstan (100). [edit]Uses Some 77% worldwide is used as a weighting agent for drilling fluids in oil and gas exploration to suppress high formation pressures and prevent blowouts. As a well is drilled, the bit passes through various formations, each with different characteristics. The deeper the hole, the more barite is needed as a percentage of the total mud mix. An additional benefit of barite is that it is non-magnetic and thus does not interfere with magnetic measurements taken in the borehole, either during logging-while-drilling or in separate drill hole logging. Barite used for drilling petroleum wells can be black, blue, brown or gray depending on the ore body. The barite is finely ground so that at least 97% of the material, by weight, can pass through a 200-mesh (75-m) screen, and no more than 30%, by weight, can be less than 6 m diameter. The ground barite also must be dense enough so that its specific gravity is 4.2 or greater, soft enough to not damage the bearings of a tricone drill bit, chemically inert, and containing no more than [7] 250 milligrams per kilogram of soluble alkaline salts. Other uses are in added-value applications which include filler in paint and plastics, sound reduction in engine compartments, coat of automobile finishes for smoothness and corrosion resistance, friction products for automobiles and trucks, radiation-shielding cement, glass ceramics and medical applications (for example, a barium meal before a contrast CAT scan). Baryte is supplied in a variety of forms and the price depends on the amount of processing; filler applications commanding higher prices following intense physical processing by grinding and micronising, and there are further premiums for whiteness [7] and brightness and color. Historically baryte was used for the production of barium hydroxide for sugar refining, and as a [2] white pigment for textiles, paper, and paint. Although baryte contains a "heavy" metal (barium), it is not considered to be a toxic chemical by most governments because of its extreme insolubility. [edit]Paleothermometry

Baryte with Cerussite from Morocco

In the deep ocean, away from continental sources of sediment, pelagic baryte crystallizes out and forms a 18 significant amount of the sediments. Since baryte has oxygen, systematics in the O of these sediments have been used to help constrain paleotemperatures for oceanic crust. Similarly the variations in sulfur [13] isotopes are also being exploited.

BERYL

In geology, beryl is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be3Al2(SiO3)6. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white. [edit]Etymology The name beryl is derived (via Latin: beryllus, Old French: beryl, and Middle English: beril) [1] from Greek beryllos which referred to a "precious blue-green color-of-sea-water stone" and originated from Prakrit veruliya ( ) and Pali veuriya ( ); veiru ( ); from Sanskrit vaidurya-, which is ultimately of Dravidian origin, maybe from the name of Belur or "Velur" in [4] [2] southern India. The term was later adopted for the mineral beryl more exclusively. The Late Latin word berillus was abbreviated as brill- which produced the Italian word brillare meaning "shine", theFrench word brille meaning "shine", the Spanish word brillo, also meaning "shine", and [5] the English word brilliance. [edit]Deposits

Beryl of various colors is found most commonly in granitic pegmatites, but also occurs in mica schists in the Ural Mountains, and limestone inColombia. Beryl is often associated with tin and tungsten ore bodies. Beryl is found in Europe in Norway, Austria, Germany, Sweden (especially morganite), Ireland and Russia, as well as Brazil, Colombia, Madagascar, Mozambique, South Africa, the United States, and Zambia. U.S. beryl locations are in California, Colorado, Connecticut, Idaho, Maine, New Hampshire, North Carolina, South Dakota and Utah. New England's pegmatites have produced some of the largest beryls found, including one massive crystal from the Bumpus Quarry in Albany, Mainewith dimensions 5.5 m by 1.2 m (18 ft by 4 ft) with a mass of around 18 metric tons; it is New Hampshire's state mineral. As of 1999, the world's largest known naturally occurring crystal of any mineral is a crystal of beryl from Malakialina, Madagascar, 18 meters [6] long and 3.5 meters in diameter, and weighing 380,000 kilogrammes. [edit]Varieties [edit]Aquamarine

and maxixe

Aquamarine

Aquamarine (from Latin: aqua marina, "water of the sea") is a blue or turquoise variety of beryl. It occurs at most localities which yield ordinary beryl. The gem-gravel placer deposits of Sri Lanka contain aquamarine. Clear yellow beryl, such as that occurring in Brazil, is sometimes called aquamarine [citation needed] chrysolite. The deep blue version of aquamarine is calledmaxixe. Maxixe is commonly found in the country of Madagascar. Its color fades to white when exposed to sunlight or is subjected to heat treatment, though the color returns with irradiation. The pale blue color of aquamarine is attributed to Fe . The Fe ions produce golden-yellow color, and 2+ 3+ when both Fe and Fe are present, the color is a darker blue as in maxixe. Decoloration of maxixe by 3+ 2+ [7][8][9][10] light or heat thus may be due to the charge transfer Fe and Fe . Dark-blue maxixe color can be produced in green, pink or yellow beryl by irradiating it with high-energy particles (gamma [11] rays, neutrons or even X-rays). In the United States, aquamarines can be found at the summit of Mt. Antero in the Sawatch Range in central Colorado. InWyoming, aquamarine has been discovered in the Big Horn Mountains, near Powder River Pass. In Brazil, there are mines in the states of Minas Gerais, Esprito Santo, and Bahia, and2+ 3+

minorly in Rio Grande do Norte. The mines of Colombia, Zambia, Madagascar, Malawi,Tanzania and Kenya also produce aquamarine. The largest aquamarine of gemstone quality ever mined was found in Marambaia, Minas Gerais, Brazil, in 1910. It weighed over 110 kg, and its dimensions were 48.5 cm (19 in) long and 42 cm (17 in) in [12] diameter. The largest cut aquamarine gem is the Dom Pedro aquamarine, now housed in [13] the Smithsonian Institution's National Museum of Natural History. [edit]Emerald Main article: Emerald

Rough emerald on matrix

Emerald refers to green beryl, colored by trace amounts of chromium and sometimes vanadium. The word "emerald" comes (via Middle English: Emeraude, imported from Old French: smeraude and Medieval Latin: Esmaraldus) from Latin smaragdus from Greek smaragdos ("green gem"), its original source being a Semitic word izmargad ( )or the Sanskrit word, marakata ( ), meaning "green". Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor. Emeralds in antiquity were mined by the Egyptians and in Austria, as well as Swat in [16] northern Pakistan. A rare type of emerald known as a trapiche emerald is occasionally found in the mines of Colombia. A trapiche emerald exhibits a "star" pattern; it has raylike spokes of dark carbon impurities that give the emerald a six-pointed radial pattern. It is named for the trapiche, a grinding wheel used to process sugarcane in the region. Colombian emeralds are generally the most prized due to their transparency and fire. Some of the most rare emeralds come from three main emerald mining areas in Colombia: Muzo, Coscuez, and Chivor. Fine emeralds are also found in other countries, such as Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. In the US, emeralds can be found in Hiddenite, North Carolina. In 1998, emeralds were discovered in the Yukon. Emerald is a rare and valuable gemstone and, as such, it has provided the incentive for developing [17] synthetic emeralds. Both hydrothermal and flux-growth synthetics have been produced. The first [18] commercially successful emerald synthesis process was that of Carroll Chatham. The other large producer of flux emeralds was Pierre Gilson Sr., which has been on the market since 1964. Gilson's emeralds are usually grown on natural colorless beryl seeds which become coated on both sides. Growth occurs at the rate of 1 mm per month, a typical seven-month growth run producing emerald crystals of [19] 3+ [8][9][10] 7 mm of thickness. The green color of emeralds is attributed to presence of Cr ions.[15]

[7][14]

Golden beryl

Heliodor

[edit]Golden

beryl and heliodor

Golden beryl can range in colors from pale yellow to a brilliant gold. Unlike emerald, golden beryl has very few flaws. The term "golden beryl" is sometimes synonymous with heliodor (from Greek hlios "sun" + dron "gift") but golden beryl refers to pure yellow or golden yellow shades, while 3+ [7][8] heliodor refers to the greenish-yellow shades. The golden yellow color is attributed to Fe ions. Both golden beryl and heliodor are used as gems. Probably the largest cut golden beryl is the flawless [20] 2054 carat stone on display in the Hall of Gems, Washington, D.C. [edit]Goshenite

Goshenite

Colorless beryl is called goshenite. The name originates from Goshen, Massachusetts where it was originally discovered. Since all these color varieties are caused by impurities and pure beryl is colorless, it might be tempting to assume that goshenite is the purest variety of beryl. However, there are several elements that can act as inhibitors to color in beryl and so this assumption may not always be true. The name goshenite has been said to be on its way to extinction and yet it is still commonly used in the gemstone markets. Goshenite is found to some extent in almost all beryl localities. In the past, goshenite was used for manufacturing eyeglasses and lenses owing to its transparency. Nowadays, it is most [21][22] commonly used for gemstone purposes and also considered as a source of beryllium.

The gem value of goshenite is relatively low. However, goshenite can be colored yellow, green, pink, blue and in intermediate colors by irradiating it with high-energy particles. The resulting color depends on the [8] content of Ca, Sc, Ti, V, Fe, and Co impurities. [edit]Morganite

Morganite

Morganite, also known as "pink beryl", "rose beryl", "pink emerald", and "cesian (or caesian) beryl", is a rare light pink to rose-colored gem-quality variety of beryl. Orange/yellow varieties of morganite can also be found, and color banding is common. It can be routinely heat treated to remove patches of yellow and is occasionally treated by irradiation to improve its color. The pink color of morganite is attributed to 2+ [7] Mn ions. Pink beryl of fine color and good sizes was first discovered on an island on the coast of Madagascar in [23] 1910. It was also known, with other gemstone minerals, such astourmaline and kunzite, at Pala, California. In December 1910, the New York Academy of Sciences named the pink variety of beryl [23] "morganite" after financier J. P. Morgan. On October 7, 1989, one of the largest gem morganite specimens ever uncovered, eventually called "The [24] Rose of Maine," was found at the Bennett Quarry in Buckfield,Maine, USA. The crystal, originally somewhat orange in hue, was 23 cm (9 in) long and about 30 cm (12 in) across, and weighed (along with [25] its matrix) just over 50 lbs (23 kg). [edit]Red

beryl

Red beryl

Red beryl (also known as "red emerald" or "scarlet emerald") is a red variety of beryl. It was first described in 1904 for an occurrence, its type locality, at Maynard's Claim (Pismire Knolls), Thomas [26][27] Range, Juab County, Utah. The old synonym "bixbite" is deprecated from the CIBJO, because of the

risk of confusion with the mineralbixbyite (also named after the mineralogist Maynard Bixby). The dark red 3+ [7] color is attributed to Mn ions. Red beryl is very rare and has only been reported from a handful of locations including: Wah Wah Mountains, Beaver County, Utah; Paramount Canyon and Round Mountain,Sierra County, New [1] Mexico; and Juab County, Utah. The greatest concentration of gem-grade red beryl comes from the Violet Claim in the Wah Wah Mountains of mid-western Utah, discovered in 1958 by Lamar Hodges, [28] of Fillmore, Utah, while he was prospecting for uranium. Prices for top quality natural red beryl can be as high as $10,000 per carat for faceted stones. Red beryl has been known to be confused with pezzottaite, also known as raspberry beryl or "raspberyl", a gemstone that has been found in Madagascar and now Afghanistan although cut gems of the two varieties can be distinguished from [29] their difference in refractive index. While gem beryls are ordinarily found in pegmatites and certain metamorphic stones, red beryl occurs in topaz-bearing rhyolites. It formed by crystallizing under low pressure and high temperature from a pneumatolitic phase along fractures or within near-surface miarolitic cavities of the rhyolite. Associated [30] minerals include bixbyite, quartz,orthoclase, topaz, spessartine, pseudobrookite and hematite.

Beryl

Three varieties of beryl: morganite, aquamarine and heliodor

General

Category

Silicate mineral

Formula(repeating unit)

Be3Al2(SiO3)6

Strunz classification

9.CJ.05

Crystal symmetry

Hexagonal dihexagonal dipyramidal H-M symbol (6/m 2/m 2/m) Space group: P 6/mmc

Unit cell

a = 9.21 , c = 9.19 ; Z = 2

Identification

Formula mass

537.50

Color

Green, blue, yellow, colorless, pink and others

Crystal habit

Prismatic to tabular cystals; radial, columnar; granular to compact massive

Crystal system

Hexagonal

Twinning

Rare

Cleavage

Imperfect on {0001}

Fracture

Conchoidal to irregular

Tenacity

Brittle

Mohs scalehardness

7.58

Luster

Vitreous to resinous

Streak

White

Diaphaneity

Transparent to translucent

Specific gravity

Average 2.76

Optical properties

Uniaxial (-)

Refractive index

n = 1.5641.595 n = 1.5681.602

Birefringence

= 0.00400.0070

Pleochroism

Weak to distinct

Ultravioletfluorescence None (some fracture filling materials used to improve emerald's clarity do fluoresce, but the stone itself does not)

BIOTITE (MICA)

Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K(Mg,Fe)3AlSi3O10(F,OH)2. More generally, it refers to the dark mica series, primarily a solidsolution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers include siderophyllite. Biotite was named by J.F.L. Hausmann in 1847 in honour of the French physicist Jean-Baptiste Biot, who, in 1816, researched the optical properties of mica, [4] discovering many unique properties. Biotite is a sheet silicate. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich

than phlogopite. It is also sometimes called "black mica" as opposed to "white mica" (muscovite) both form in some rocks, in some instances side-by-side. [edit]Properties Like other mica minerals, biotite has a highly perfect basal cleavage, and consists of flexible sheets, or lamellae, which easily flake off. It has amonoclinic crystal system, with tabular to prismatic crystals with an obvious pinacoid termination. It has four prism faces and two pinacoid faces to form a pseudohexagonal crystal. Although not easily seen because of the cleavage and sheets, fracture is uneven. It appears greenish to brown or black, and even yellow when weathered. It can be transparent to opaque, has a vitreous to pearly luster, and a grey-white streak. When biotite is found in large chunks, they are called books because it resembles a book with pages of many sheets. Under cross-polarized light biotite can generally be identified by the gnarled bird's eye extinction. [edit]Occurrence Biotite is found in a wide variety of igneous and metamorphic rocks. For instance, biotite occurs in the lava of Mount Vesuvius and in the Monzoni intrusive complex of the western Dolomites. It is an essential phenocryst in some varieties of lamprophyre. Biotite is occasionally found in large cleavable crystals, especially in pegmatite veins, as in New England, Virginia and North Carolina. Other notable occurrences include Bancroft andSudbury, Ontario. It is an essential constituent of many metamorphic schists, and it forms in suitable compositions over a wide range of pressure andtemperature. The largest documented single crystals of biotite were approximately 7 m (75 sq ft) sheets found [5] in Iveland, Norway. [edit]Uses2

biotite: Topotype deposit

Biotite is used extensively to constrain ages of rocks, by either potassium-argon dating or argon-argon dating. Because argon escapes readily from the biotite crystal structure at high temperatures, these methods may provide only minimum ages for many rocks. Biotite is also useful in assessing temperature histories of metamorphic rocks, because the partitioning of iron and magnesium between biotite and garnetis sensitive to temperature.

Biotite

thin tabular Biotite aggregate (Image width: 2.5 mm)

General

Category

Dark Mica series

Formula(repeating unit)

K(Mg,Fe)3(AlSi3O10)(F,OH)2

Identification

Formula mass

433.53 g

Color

Dark brown, greenish brown, blackish brown, yellow, white

Crystal habit

massive to platy

Crystal system

Monoclinic (2/m) Space Group: C 2/m

Twinning

common on the [310], less common on the {001}

Cleavage

Perfect on the {001}

Fracture

Micaceous

Tenacity

Brittle to flexible, elastic

Mohs scalehardness

2.53.0

Luster

Vitreous to pearly

Streak

White

Diaphaneity

transparent to translucent to opaque

Specific gravity

2.73.1

Density

2.83.4

Optical properties

Biaxial (-)

Refractive index

n = 1.5651.625 n = 1.6051.675 n = 1.6051.675

Birefringence

= 0.030.07

Pleochroism

strong

Dispersion

r < v (Fe rich); r > v weak (Mg rich)

Ultravioletfluorescence None

BORNITE

Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the orthorhombic system (pseudo-cubic). [edit]Appearance

Tarnish of Bornite

Bornite has a brown to copper-red color on fresh surfaces that tarnishes to various iridescent shades of blue to purple in places. Its striking iridescence gives it the nickname peacock copper or peacock ore. [edit]Mineralogy Bornite is an important copper ore mineral and occurs widely in porphyry copper deposits along with the more common chalcopyrite. Chalcopyrite and bornite are both typically replaced by chalcocite andcovellite in the supergene enrichment zone of copper deposits. Bornite is also found as disseminations inmafic igneous rocks, in contact metamorphic skarn deposits, in pegmatites and [2] in sedimentarycupriferous shales. It is important as an ore for its copper content of about 63 percent by [1] mass. [edit]Occurrence

Bornite with silver from Zacatecas,Mexico (size: 7.5 x 4.3 x 3.4 cm)

It occurs globally in copper ores with notable crystal localities in Butte, Montana and at Bristol,Connecticut in the U. S. It is also collected from the Carn Brea mine, Illogan, and elsewhere in Cornwall,England. Large crystals are found from the Frossnitz Alps, eastern Tirol, Austria; the Mangula mine,Lomagundi district, Zimbabwe; from the Nouva mine, Talate, Morocco, the West Coast of Tasmania [2] and in Dzhezkazgan, Kazakhstan. [edit]History

and etymology

It was first described in 1725 for an occurrence in the Krun Hory Mountains ( Erzgebirge), Karlovy Vary Region, Bohemia in what is now the Czech Republic. It was named in 1845 for Austrian mineralogistIgnaz [3] von Born (17421791).

CALCITE

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). The other [5] polymorphs are the minerals aragonite andvaterite. Aragonite will change to calcite at 380-470C, and vaterite is even less stable. [edit]Properties Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals. However, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain. It has a defining Mohs hardness of 3, a specific gravity of 2.71, and its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities. Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar" while the rhombohedral form is sometimes referred to as "nailhead spar". Single calcite crystals display an optical property called birefringence (double refraction). This strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect (using calcite) was first described by the Danish scientist Rasmus Bartholin in 1669. At a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, [6] respectively. Between 190 and 1700 nm, the ordinary refractive index varies roughly between 1.6 and [7] 1.4, while the extraordinary refractive index varies between 1.9 and 1.5. Calcite, like most carbonates, will dissolve with most forms of acid. Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Although calcite is fairly insoluble in cold water, acidity can cause dissolution of calcite and release of carbon dioxide gas. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When

conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. When conditions are right for dissolution, the removal of calcite can dramatically increase the porosity and permeability of the rock, and if it continues for a long period of time may result in the formation of caves. On a landscape scale, continued dissolution of calcium carbonaterich rocks can lead to the expansion and eventual collapse of cave systems, resulting in various forms of karst topography. [edit]Use

and applications

High-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti[8] [9] aircraft weaponry. Also, experiments have been conducted to use calcite for a cloak of invisibility. [edit]Natural

occurrence

The largest documented single crystals of calcite originated from Iceland, measured 772 m and 663 [10][11] m and weighed about 250 tons.

Doubly terminated calcite crystal

Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms. Approximately 10% of sedimentary rock is limestone. Calcite is the primary mineral in metamorphic marble. It also occurs as a vein mineral in deposits from hot springs, and it occurs in caverns asstalactites and stalagmites. Lublinite is a fibrous, efflorescent form of calcite.[12]

Calcite may also be found in volcanic or mantle-derived rocks such as carbonatites, kimberlites, or rarely in peridotites. Calcite is often the primary constituent of the shells of marine organisms, e.g., plankton (such ascoccoliths and planktic foraminifera), the hard parts of red algae, some sponges, brachiopods,echinoderms, some serpulids, most bryozoa, and parts of the shells of some bivalves (such as oystersand rudists). Calcite is found in spectacular form in the Snowy River Cave of New Mexico as mentioned above, where microorganisms are credited with natural formations. Trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes. [edit]Calcite

formation processes

Calcite forms from a poorly ordered precursor (amorphous calcium carbonate, ACC). The crystallization process occurs in two stages; firstly, the ACC nanoparticles rapidly dehydrate and crystallize to form individual particles of vaterite; secondly, the vaterite transforms to calcite via a dissolution and reprecipitation mechanism with the reaction rate controlled by the surface area of [14] calcite. The second stage of the reaction is approximately 10 times slower than the rst. However, the crystallization of calcite has been observed to be dependent on the starting pH and presence of Mg in [15] solution. A neutral starting pH during mixing promotes the direct transformation of ACC into calcite. Conversely, when ACC forms in a solution that starts with a basic initial pH, the transformation to calcite [16] occurs via metastable vaterite, which forms via a spherulitic growth mechanism. In a second stage this vaterite transforms to calcite via a surface-controlled dissolution and recrystallization mechanism. Mg has a noteworthy effect on both the stability of ACC and its transformation to crystalline CaCO3, resulting in the formation of calcite directly from ACC, as this ion unstabilizes the structure of vaterite. [edit]Calcite

[13]

in Earth history

Calcite seas existed in Earth history when the primary inorganic precipitate of calcium carbonate in marine waters was low-magnesium calcite (lmc), as opposed to the aragonite and high-magnesium calcite (hmc) precipitated today. Calcite seas alternated with aragonite seas over the Phanerozoic, being most prominent in the Ordovician and Jurassic. Lineages evolved to use whichever morph of calcium carbonate was favourable in the ocean at the time they became mineralised, and retained this mineralogy [17] for the remainder of their evolutionary history. Petrographic evidence for these calcite sea conditions consists of calcitic ooids, lmc cements, hardgrounds, and rapid early seafloor aragonite [18] dissolution. The evolution of marine organisms with calcium carbonate shells may have been affected [19] by the calcite and aragonite sea cycle.

Calcite

A one-inch calcite rhomb that shows the double image refraction property

General

Category

Carbonate mineral

Formula(repeating unit)

CaCO3

Strunz classification

05.AB.05

Crystal symmetry

Trigonal 32/m

Unit cell

a = 4.9896(2) , c = 17.0610(11) ; Z=6

Identification

Color

Colorless or white, also gray, yellow, green,

Crystal habit

Crystalline, granular, stalactitic, concretionary, massive, rhombohedral.

Crystal system

Trigonal hexagonal scalenohedral (32/m), Space Group (R3 2/c)

Twinning

Common by four twin laws

Cleavage

Perfect on [1011] three directions with angle of 74 55'[1]

Fracture

Conchoidal

Tenacity

Brittle

Mohs scalehardness

3 (defining mineral)

Luster

Vitreous to pearly on cleavage surfaces

Streak

White

Diaphaneity

Transparent to translucent

Specific gravity

2.71

Optical properties

Uniaxial (-)

Refractive index

n = 1.640 1.660 n = 1.486

Birefringence

= 0.154 0.174

Solubility

Soluble in dilute acids

Other characteristics

May fluoresce red, blue, yellow, and other colors under either SW and LW UV; phosphorescent

CELESTITE

Celestine or celestite (SrSO4) is a mineral consisting of strontium sulfate. The mineral is named for its occasional delicate blue color. Celestine is the principal source of the element strontium, commonly used in fireworks and in various metal alloys. [edit]Occurrence

[4]

Celestine from the Machow Mine, Poland.

Celestine occurs as crystals, and also in compact massive and fibrous forms. It is mostly found insedimentary rocks, often associated with the minerals gypsum, anhydrite, and halite.

The mineral is found worldwide, usually in small quantities. Pale blue crystal specimens are found inMadagascar. The skeletons of the protozoan Acantharea are made of celestine, unlike those of other radiolarians which are made of silica. In carbonate marine sediments, burial dissolution is a recognised mechanism of celestine precipitation. [edit]Geodes[5]

Celestine geode section

Inside the Crystal Cave geode in Ohio

Celestine crystals are found in some geodes. The world's largest known geode, a celestine geode 35 feet (10.7 m) in diameter at its widest point, is located near the village of Put-in-Bay, Ohio, on South Bass Island in Lake Erie. The geode has been converted into a viewing cave, Crystal Cave, with the crystals which once composed the floor of the geode removed. The geode has celestine crystals as wide as 18 inches (46 cm) across, estimated to weigh up to 300 pounds (135 kg) each.

Celestine

Clear grey-blue celestine crystal crust from Madagascar

General

Category

Sulfate minerals

Formula(repeating unit)

SrSO4 sometimes contains minor calcium and/or barium

Strunz classification

07.AD.35

Crystal symmetry

Orthorhombic 2/m 2/m 2/m dipyramidal

Unit cell

a = 8.359 , b = 5.352 , c = 6.866 ; Z =4

Identification

Color

Colorless, white, pale blue, pink, pale green, pale brown, black

Crystal habit

Tabular to pyramidal crystals, also fibrous, lamellar, earthy, massive granular

Crystal system

Orthorhombic

Cleavage

Perfect on {001}, good on {210}, poor on {010}

Fracture

Uneven

Tenacity

Brittle

Mohs scalehardness

3 - 3.5

Luster

Vitreous, pearly on cleavages

Streak

white

Diaphaneity

Transparent to translucent

Specific gravity

3.95 - 3.97

Optical properties

Biaxial (+)

Refractive index

n = 1.619 - 1.622 n = 1.622 - 1.624 n = 1.630 - 1.632

Birefringence

= 0.011

Pleochroism

Weak

2V angle

Measured: 50 to 51

Dispersion

Moderate r < v

Ultravioletfluorescence Short UV=yellow, white blue, long UV=yellow, white blue

CHALCOPYRITE

Chalcopyrite (pron.: /klkparat/ KAL-ko-PY-ryt) is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical composition CuFeS2. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black. On exposure to air, chalcopyrite oxidises to a variety of oxides, hydroxides and sulfates. Associated copper minerals include the sulfides bornite(Cu5FeS4), chalcocite (Cu2S), covellite (CuS), digenite (Cu9S5); carbonates such as malachite and azurite, and rarely oxides such as cuprite(Cu2O). Chalcopyrite is rarely found in association with native copper. [edit]Chemistry

The unit cell of chalcopyrite. Copper is shown in pink, iron in blue and sulfur in yellow.

Natural chalcopyrite has no solid solution series with any other sulfide minerals. There is limited substitution of Zn with Cu despite chalcopyrite having the same crystal structure as sphalerite. However, it is often contaminated by a variety of other trace elements such as Co, Ni, Mn, Zn and Sn substituting for Cu and Fe. Se, Fe and As substitute for sulfur, and trace amounts of Ag, Au, Pt, Pd, Pb, V, Cr, In, and Sb are reported. It is likely many of these elements are present in finely intergrown minerals within the chalcopyrite crystal, for instance lamellae of arsenopyriterepresenting As, molybdenite representing Mo, etc. [edit]Paragenesis Chalcopyrite is present with many ore bearing environments via a variety of ore forming processes. Chalcopyrite is present in volcanogenic massive sulfide ore deposits and sedimentary exhalative deposits, formed by deposition of copper duringhydrothermal circulation. Chalcopyrite is concentrated in this environment via fluid transport. Porphyry copper ore deposits are formed by concentration of copper within a granite stock during the ascent and crystallisation of a magma. Chalcopyrite in this environment is produced by concentration within a magmatic system. Chalcopyrite is an accessory mineral in Kambalda type komatiitic nickel ore deposits, formed from an immiscible sulfide liquid in sulfur-saturated ultramafic lavas. In this environment chalcopyrite is formed by a sulfide liquid stripping copper from an immiscible silicate liquid. [edit]Occurrence

Fine brassy chalcopyrite crystals below large striated pyrite cubes (size:8.8 x 6.3 x 4.5 cm)

Chalcopyrite is the most important copper ore. Chalcopyrite ore occurs in a variety of ore types, from huge masses as at Timmins, Ontario, to irregular veins and disseminations associated with granitic to dioritic intrusives as in the porphyry copper deposits of Broken Hill, the American cordillera and the Andes. The largest deposit of nearly pure chalcopyrite ever discovered in Canada was at the southern end of the Temagami greenstone belt where Copperfields Mine extracted the high-grade [6] copper. Chalcopyrite is present in the supergiant Olympic Dam Cu-Au-U deposit in South Australia.

Chalcopyrite may also be found in coal seams associated with pyrite nodules, and as disseminations in carbonate sedimentary rocks. [edit]Structure Crystallographically the structure of chalcopyrite is closely related to that of zinc blende ZnS (sphalerite). + 3+ 2+ The unit cell is twice as large, reflecting an alternation of Cu and Fe ions replacing Zn ions in adjacent 2cells. In contrast to the pyrite structure chalcopyrite has single S sulfide anions rather than disulfide pairs. Another difference is that the iron cation is not diamagnetic low spin Fe(II) as in pyrite.

Chalcopyrite

Twinned chalcopyrite crystal from the Camp Bird Mine, Ouray County, Colorado. Crystal is about 1 cm x 1 cm.

General

Category

Sulfide mineral

Formula(repeating unit)

CuFeS2

Strunz classification

02.CB.10a

Crystal symmetry

Tetragonal 42m scalenohedral

Unit cell

a = 5.289 , c = 10.423 ; Z = 4

Identification

Formula mass

183.54

Color

Brass yellow, may have iridescent purplish tarnish.

Crystal habit

Predominantly the disphenoid and resembles a tetrahedron, commonly massive, and sometimes botryoidal.

Crystal system

Tetragonal Scalenohedral 42m

Twinning

Penetration twins

Cleavage

Indistinct on {011}

Fracture

Irregular to uneven

Tenacity

Brittle

Mohs scalehardness

3.5

Luster

Metallic

Streak

Greenish black

Diaphaneity

Opaque

Specific gravity

4.1 4.3

Solubility

Soluble in HNO3

Other characteristics

magnetic on heating

COPPER

Copper is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal andelectrical conductivity. Pure copper is soft and malleable; a freshly exposed surface has a reddish-orange color. It is used as a conductor of heat and electricity, a building material, and a constituent of various metal alloys. The metal and its alloys have been used for thousands of years. In the Roman era, copper was principally mined on Cyprus, hence the origin of the name of the metal as yprium (metal of Cyprus), later shortened to uprum. Its compounds are commonly encountered as copper(II) salts, which often impart blue or green colors to minerals such as azurite and turquoise and have been widely used historically as pigments. Architectural structures built with copper corrode to give green verdigris (or patina). Decorative art prominently features copper, both by itself and as part of pigments. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustacea copper is a constituent of the blood pigment hemocyanin, which is replaced by the iron-complexed hemoglobinin fish and other [citation vertebrates. The main areas where copper is found in vertebrate animals are liver, muscle and bone. needed] In sufficient concentration, copper compounds are poisonous to higher organisms and are used as bacteriostatic substances, fungicides, and wood preservatives.

Characteristics

Physical

A copper disc (99.95% pure) made by continuous casting and etching.

Copper just above its melting point keeps its pink luster color when enough light outshines the orange incandescence color.

Copper, silver and gold are in group 11 of the periodic table, and they share certain attributes: they have one s-orbital electron on top of a filled d-electron shell and are characterized by high ductility and electrical conductivity. The filled d-shells in these elements do not contribute much to the interatomic interactions, which are dominated by the s-electrons through metallic bonds. Contrary to metals with incomplete d-shells, metallic bonds in copper are lacking acovalent character and are relatively weak. [2] This explains the low hardness and high ductility of single crystals of copper. At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress thereby increasing its hardness. For this reason, copper is usually supplied [3] in a fine-grained polycrystalline form, which has greater strength than monocrystalline forms. The low hardness of copper partly explains its high electrical conductivity (59.610 S/m) and thus also [4] high thermal conductivity, which are the second highest among pure metals at room temperature. This is because the resistivity to electron transport in metals at room temperature mostly originates from [2] scattering of electrons on thermal vibrations of the lattice, which are relatively weak for a soft metal. The 6 2 maximum permissible current density of copper in open air is approximately 3.110 A/m of cross[5] sectional area, above which it begins to heat excessively. As with other metals, if copper is placed [6] against another metal, galvanic corrosion will occur. Together with caesium and gold (both yellow), and osmium (bluish), copper is one of only four elemental [7] metals with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells the energy difference between these6

shells is such that it corresponds to orange light. The same mechanism accounts for the yellow color of [2] gold and caesium.

Chemical

Unoxidized copper wire (left) and oxidized copper wire (right).

The East Tower of the Royal Observatory, Edinburgh. The contrast between the refurbished copper installed in 2010 and the green color of the original 1894 copper is clearly seen.

Copper forms a rich variety of compounds with oxidation states +1 and +2, which are often [8] called cuprous and cupric, respectively. It does not react with water, but it slowly reacts with atmospheric oxygen forming a layer of brown-black copper oxide. In contrast to the oxidation of iron by wet air, this oxide layer stops the further, bulk corrosion. A green layer of verdigris (copper carbonate) can often be seen on old copper constructions, such as the Statue of Liberty, the largest copper statue in the [9] world built using repouss and chasing. Copper tarnishes when exposed tohydrogen sulfides and [10] other sulfides, which react with it to form various copper sulfides on the surface. Oxygen-containing ammonia solutions give water-soluble complexes with copper, as do oxygen and hydrochloric acid to form copper chlorides and acidified hydrogen peroxide to form copper(II) salts. Copper(II) chloride and [11] coppercomproportionate to form copper(I) chloride.

IsotopesMain article: Isotopes of copper

There are 29 isotopes of copper. Cu and Cu are stable, with Cu comprising approximately 69% of [12] naturally occurring copper; they both have a spin of 3/2. The other isotopes are radioactive, with the 67 [12] most stable being Cu with a half-life of 61.83 hours. Seven metastable isotopes have been 68m characterized, with Cu the longest-lived with a half-life of 3.8 minutes. Isotopes with a mass + 64 number above 64 decay by , whereas those with a mass number below 64 decay by . Cu, which has [13] a half-life of 12.7 hours, decays both ways.62

63

65

63

Cu and Cu have significant applications. Cu is a radiocontrast agent for X-ray imaging, and 62 62 complexed with a chelate can be used for treatingcancer. Cu is used in Cu-PTSM that is a radioactive [14] tracer for positron emission tomography.

64

64

OccurrenceCopper is synthesized in massive stars and is present in the Earth's crust at a concentration of about [16] 50 parts per million (ppm), where it occurs as native copper or in minerals such as the copper sulfides chalcopyrite and chalcocite, copper carbonates azurite and malachite and thecopper(I) [4] oxide mineral cuprite. The largest mass of elemental copper discovered weighed 420 tonnes and was [16] found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal, with the [17] largest described single crystal measuring 4.43.23.2 cm.[15]

CORUNDUM

Corundum is a crystalline form of aluminium oxide (Al2O3) with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, calledruby if red and padparadscha if pink-orange. All other colors are called sapphire, e.g., "green sapphire" for a green specimen. The name "corundum" is derived from the Tamil word kuruntam ( to Sanskrit kuruvinda.[3]

[1]

) meaning "ruby", and related

Because of corundum's hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral. It is commonly used as anabrasive, on everything from sandpaper to large machines used in machining metals, plastics, and wood. Some emery is a mix of corundum and other substances, and the mix is less abrasive, with an average hardness near 8.0. In addition to its hardness, corundum is unusual for its density of 4.02 g/cm , which is very high for a [5] transparent mineral composed of the lowatomic mass elements aluminium and oxygen. [edit]Geology3

and occurrence

Corundum from Brazil, size about 2 by 3 centimetres (0.8 in 1 in).

Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. It also occurs in low silica igneous syenite and nepheline syenite intrusives. Other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals [4] in pegmatites. It commonly occurs as a detrital mineral in stream and beach sands because of its [4] hardness and resistance to weathering. The largest documented single crystal of corundum measured [6] about 65 40 40 centimetres (26 16 16 in). Corundum for abrasives is mined in Zimbabwe, Russia, Sri Lanka and India. Historically it was mined from deposits associated with dunites in North Carolina, USA and from a nepheline syenite in Craigmont, [4] Ontario. Emery grade corundum is found on the Greek island of Naxos and near Peekskill, New York, [4] USA. Abrasive corundum is synthetically manufactured from bauxite. Corundum should not be confused with the similarly named carborundum, silicon carbide. [edit]Synthetic

corundum

In 1837, Marc Antoine Gaudin made the first synthetic rubies by fusing alumina at a high temperature with [7] a small amount of chromium as a pigment. In 1847, Ebelmen made white sapphires by fusing alumina in boric acid. In 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little chromium at temperatures above 2,000 C (3,632 F). In 1903, Verneuil announced he could [8] produce synthetic rubies on a commercial scale using this flame fusion process.

Crystal structure of corundum

The Verneuil process allows the production of flawless single-crystal sapphires, rubies and other corundum gems of much larger size than normally found in nature. It is also possible to grow gem-quality synthetic corundum by flux-growth and hydrothermal synthesis. Because of the simplicity of the methods involved in corundum synthesis, large quantities of these crystals have become available on the market causing a significant reduction of price in recent years. Apart from ornamental uses, synthetic corundum is also used to produce mechanical parts (tubes, rods, bearings, and other machined parts), scratchresistant optics, scratch-resistant watch crystals, instrument windows for satellites and spacecraft (because of its transparency from the UV to IR), and laser components.

Corundum

General

Category

Oxide mineral Hematite group

Formula(repeating unit)

Aluminium oxide, Al2O3

Strunz classification

04.CB.05

Dana classification

4.3.1.1

Crystal symmetry

Trigonal (32/m)

Unit cell

a = 4.75 , c = 12.982 ; Z=6

Identification

Color

Colorless, gray, brown; pink to pigeon-blood-red, orange, yellow, green, blue to cornflower blue, violet; may be color zoned, asteriated mainly grey and brown

Crystal habit

Steep bipyramidal, tabular, prismatic, rhombohedral crystals, massive or granular

Crystal system

Trigonal (Hexagonal Scalenohedral) Symbol (32/m) Space group: R3c

Twinning

Polysynthetic twinning common

Cleavage

None parting in 3 directions

Fracture

Conchoidal to uneven

Mohs scalehardness

9 (defining mineral)

Luster

Adamantine to vitreous

Streak

White

Diaphaneity

Transparent, translucent toopaque

Specific gravity 3.954.10

Optical properties

Uniaxial ()

Refractive index

n = 1.7671.772 n = 1.7591.763

Pleochroism

None

Melting point

2044 C

Fusibility

Infusible

Solubility

Insoluble

Alters to

May alter to mica on surfaces causing a decrease in hardness

Other characteristics

May fluoresce or phosphoresce under UV

References

[1][2][3][4]

Major varieties

Sapphire

Any color except red

Ruby

Red

Emery

Black granular corundum intimately mixed with magnetite,hematite, or hercynite

DIAMOND

Diamond

The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. Its lustrous faces also indicate that this crystal is from a primary deposit.

General

Category

Native Minerals

Formula(repeating unit)

C

Strunz classification

01.CB.10a

Identification

Formula mass

12.01 gmol1

Color

Typically yellow, brown or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple and red.

Crystal habit

Octahedral

Crystal system

Isometric-Hexoctahedral (Cubic)

Cleavage

111 (perfect in four directions)

Fracture

Conchoidal (shell-like)

Mohs scalehardness

10

Luster

Adamantine

Streak

Colorless

Diaphaneity

Transparent to subtransparent to translucent

Specific gravity

3.520.01

Density

3.53.53 g/cm3

Polish luster

Adamantine

Optical properties

Isotropic

Refractive index

2.418 (at 500 nm)

Birefringence

None

Pleochroism

None

Dispersion

0.044

Melting point

Pressure dependent

DOLOMITE

Dolomite (pron.: /dlmat/) is a carbonate mineral composed of calcium magnesium carbonate CaMg(CO3)2. The term is also used to describe thesedimentary carbonate rock dolostone. Dolostone (dolomite rock) is composed predominantly of the mineral dolomite with a stoichiometric ratio of 50% or greater content of magnesium replacing calcium, often as a result of diagenesis. Limestone that is partially replaced by dolomite is referred to as dolomitic limestone, or in old U.S. geologic literature as magnesian limestone. [edit]History Dolomite was first described by the Austrian naturalist Belsazar Hacquet as the "stinking stone" [5][6] (German: Stinkstein, Latin: lapis suillus in 1778). In 1791, it was described as a rock by the French naturalist and geologist, Dodat Gratet de Dolomieu (17501801) from exposures in what are now known as the Dolomite Alps of northern Italy. The mineral was given its name in March 1792 [7] [8] by Nicolas de Saussure. Hacquet and Dolomieu met in Laibach (Ljubljana) in 1784, which may have [6] contributed to Dolomieu's work. [edit]Properties

The mineral dolomite crystallizes in the trigonal-rhombohedral system. It forms white, gray to pink, commonly curved (saddle shape) crystals, although it is usually massive. Unlike calcite, dolomite is a double carbonate, having a different structural arrangement, and it does not rapidly dissolve or effervesce (fizz) in dilute hydrochloric acid unless it is scratched or in powdered form. Crystal twinning is common. A solid solution series exists between dolomite and iron rich ankerite. Small amounts of iron in the structure give the crystals a yellow to brown tint. Manganese substitutes in the structure also up to about three percent MnO. A high manganese content gives the crystals a rosy pink color noted in the image above. A series with the manganese rich kutnohorite may exist. Lead and zinc also substitute in the structure for magnesium. It is also related to huntiteMg3Ca(CO3)4. [edit]Formation Vast deposits are present in the geological record, but the mineral is relatively rare in modern environments. Laboratory synthesis of stoichiometric dolomite has been carried out only at temperatures of greater than 100 C (conditions typical of burial in sedimentary basins), even though much dolomite in the rock record appears to have formed in low-temperature conditions. The high temperature is likely to speed up the movement of calcium and magnesium ions so that they can find their places in the ordered structure within a reasonable amount of time. This suggests that the lack of dolomite that is being formed today is likely due to kinetic factors, i.e. due to the lack of kinetic energy or temperature.

Dolomite druse from Lawrence County, Arkansas, USA (size: 24188 cm)

Modern dolomite does occur as a precipitating mineral in specialized environments on the surface of the earth today. In the 1950s and 60s, dolomite was found to be forming in highly saline lakes in the Coorong region of South Australia. Dolomite crystals also occur in deep-sea sediments, where organic matter content is high. This dolomite is termed "organogenic" dolomite. Recent research has found modern dolomite formation under anaerobic conditions in supersaturatedsaline lagoons along the Rio de Janeiro coast of Brazil, namely, Lagoa Vermelha and Brejo do Espinho. One interesting reported case was the formation of dolomite in the kidneys of [9] a Dalmatian dog. This was believed to be due to chemical processes triggered by bacteria. Dolomite has been speculated to develop under these conditions with the help of sulfate-reducing [10][11] bacteria (e.g. Desulfovibrio brasiliensis).

Dolomite.

The actual role of bacteria in the low-temperature formation of dolomite remains to be demonstrated. The specific mechanism of dolomitization, involving sulfate-reducing bacteria, has not yet been [12] demonstrated. Dolomite appears to form in many different types of environment and can have varying structural, textural and chemical characteristics. Some researchers have stated "there are dolomites and dolomites", meaning that there may not be one single mechanism by which dolomite can form. Much modern dolomite differs significantly from the bulk of the dolomite found in the rock record, leading researchers to speculate that environments where dolomite formed in the geologic past differ significantly from those where it forms today.

Dolomite bedrock underneath aBristlecone Pine, White Mountains, California.

Reproducible laboratory syntheses of dolomite (and magnesite) leads first to the initial precipitation of a metastable "precursor" (such as magnesium calcite), to be changed gradually into more and more of the stable phase (such as dolomite or magnesite) during periodical intervals of dissolution and reprecipitation. The general principle governing the course of this irreversible geochemical reaction has been coinedOstwald's step rule. For a very long time scientists had difficulties synthesizing dolomite. However, in a 1999 study, through a process of dissolution alternating with intervals of precipitation, measurable levels of dolomite were [13] synthesized at low temperatures and pressures.

[edit]Coral

atolls

Dolomitization of calcite also occurs at certain depths of coral atolls where water is undersaturated in calcium carbonate but saturated in dolomite. Convection created by tides and sea currents enhance this change. Hydrothermal currents created by volcanoes under the atoll may also play an important role. [edit]Uses

Dolomite with chalcopyrite from the Tri-state district, Cherokee County, Kansas(size: 11.47.24.6 cm)

Dolomite is used as an ornamental stone, a concrete aggregate, a source of magnesium oxide and in th