stibnite

[French stibine, stibnite (from Latin stibium, antimony; see stibine) + -ITE¹.]

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A mineral with composition Sb₂S₃ (antimony trisulfide), the chief ore of antimony. It crystallizes in slender, prismatic, vertically striated crystals which may be curved or bent. It is often in bladed, granular, or massive aggregates. The hardness is 2 on Mohs scale and the specific gravity 4.5–4.6. The luster is metallic and the color lead-gray to black. It is one of few minerals that fuses easily in the match flame (525°C or 977°F).

Stibnite has been found in various mining districts in Germany, Romania, France, Bolivia, Peru, and Mexico. In the United States the Yellow Pine mine at Stibnite, Idaho, is the largest producer. Other deposits are in Nevada and California. The finest crystals have come from the island of Shikoku, Japan. See also Antimony.

Stibnite is a lead-gray mineral (Sb₂S₃) with a metallic luster. It is the most important ore of antimony, and is also known as antimony glance. One of the few minerals that fuse easily in a match flame (977°F or 525°C), stibnite has a hardness of two on the Mohs scale and a specific gravity of 4.5 to 4.6. It is commonly found in hydrothermal veins or hot springs deposits. Stibnite is mined in Germany, Romania, France, Bolivia, Peru, and Mexico. The Yellow Pine mine at Stibnite, Idaho, is the largest producer in the United States, but California and Nevada also have deposits.

Environment

In low-temperature, often open, veins and rock impregnations. Associated with arsenic and antimony minerals.

Usually in well-formed crystals, sometimes very large and solid (Japan, China); at other times stocky and short, slender and fragile, or fibrous, massive, bladed, or granular.

Steel gray. Luster metallic; hardness 2; specific gravity 4.5-4.6; streak black; fracture subconchoidal; cleavage perfect side pinacoid.

Sulfide of antimony (71.7% Sb, 28.3% S).

Melts to a liquid, spreads out and completely volatilizes on charcoal, making a white coating around grain and weakly coloring the blowpipe flame white. Dissolves in hot concentrated HNO ₃ and slowly forms a white precipitate on addition of water.

Distinguished from lead-bearing sulfosalts by the lack of a yellow (lead oxide) coating on the surrounding charcoal and by its complete volatility. Distinguished from bismuthinite by lower gravity, more fluid fusion on charcoal, and more rapid volatilization.

An ore of antimony. Like realgar and orpiment, a late low-temperature deposit of hot solutions, often associated with the arsenic minerals and cinnabar. The finest crystals ever found were brilliant needles over a foot long (30 cm) from the Ichinokawa Mine, Iyo Province (now Ehime Prefecture), n. Shikoku I., Japan. Almost their equal are those of Xikuangshan Antimony Mine in Hunan, China. Stubbier, bluntly terminated, fine 1-2-in. (2.5-5 cm) crystals in crusts and radiating clusters come from Baia Sprie (Felsöbanya), Romania. The best U.S. crystals have been found at Manhattan, Nye Co., Nevada. A few large crystals, nearly like those of China, have been found in Huarás, Peru.

Giant ocherous pseudomorphs, now two Sb oxides--cervantite (Sb ₂ O ₄ ) and stibiconite (Sb ₃ O ₆ [OH])--give hope for some eventual fine stibnites from sources near Oaxaca, Mexico.

Stibnite is the outstanding example of a mineral showing the phenomenon of well-developed gliding planes. Slipping directions are so well developed that many of the crystals found in nature are bent, or soon become bent, without fracturing. The atoms will glide a definite distance in the basal plane and then stop. (See calcite and vivianite.)

Stibnite
Stibnite in the Carnegie Museum of Natural History
General
Category	Mineral
Chemical formula	antimony sulfide (Sb2S3)
Identification
Color	Steel gray to dull gray. Black iridescent tarnish may be present
Crystal habit	Massive, radiating and elongated crystals. Massive and granular
Crystal system	Orthorhombic, oP20, SpaceGroup = Pnma, No. 62
Cleavage	Perfect
Fracture	Small-scale subconchoidal
Mohs Scale hardness	2
Luster	Splendent on fresh crystals surfaces, otherwise metallic
Streak	Similar to color
Specific gravity	4.56–4.62
Refractive index	Opaque
Solubility	decomposed with hydrochloric acid
Major varieties
Metastibnite	Earthy, reddish deposits

Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb₂S₃. This soft grey material crystallizes in an orthorhombic space group. It is the most important source for the metalloid antimony.^[1] The abbreviation for antimony, Sb, is taken from stibnite.

Contents 1 Formation, structure, reactivity 2 Uses 3 Occurrence 4 See also 5 References

Formation, structure, reactivity

Sb₂S₃ forms when antimony(III) compounds are treated with hydrogen sulfide. This reaction gives a black precipitate:

2 Sb³⁺ + 3 H₂S → Sb₂S₃ + 6 H⁺

This reaction is reversed by hydrochloric acid.

Stibnite is attacked by potassium hydroxide solution and dissolves in solutions of polysulfide ions to give polysulfido complexes.^[2] Related reactions were once used in university courses on qualitative inorganic analysis.

Stibnite has a structure similar to that of arsenic trisulfide, As₂S₃. The Sb(III) centers, which are pyramidal and three-coordinate, are linked via bent two-coordinate sulfide ions. It is grey when fresh, but can turn superficially black due to oxidation in air.

Uses

Stibnite has no significant uses, except as a precursor to antimony oxide, which is the most commonly marketed form of antimony. In ancient times, it was used as mascara called kohl.

Antimony trisulfide finds use in pyrotechnic compositions, namely in the glitter and fountain mixtures. Needle-like crystals, "Chinese Needle", are used in glitter compositions and white pyrotechnic stars. The "Dark Pyro" version is used in flash powders to increase their sensitivity and sharpen their report. It is also a component of modern safety matches. It was formerly used in flash compositions, but its use was abandoned due to toxicity and sensitivity to static electricity.[1]

Occurrence

Stibnite specimen at the American Museum of Natural History

Small deposits of stibnite are common, but large deposits are rare. It occurs in Canada, Mexico, Peru, Japan, China, Germany, Romania, Italy, France, England, Algeria, and Kalimantan, Borneo. In the United States it is found in Arkansas, Idaho, Nevada, California, and Alaska.

As of May 2007, the largest specimen on public display (1000 pounds) is at the American Museum of Natural History.^[3][4] The largest documented single crystals of stibnite measured ~60x5x5 cm³ and originated from different locations including Japan, France and Germany.^[5]

See also

• List of minerals

References

1. ^ Sabina C. Grund, K. Hanusch, H. J. Breunig, H. U. Wolf, “Antimony and Antimony Compounds” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a03 055.pub2
2. ^ Martin, T. M.; Schimek, G. L.; Pennington, W. T. and Kolis, J. W., "Synthesis of Two New Antimony Sulfide Clusters: Structures of [PPh₄]₂[Sb₆S₆] and [PPh₄]₂[Sb₄S₆]", Journal of the Chemical Society, Dalton Transactions 1995, 501-2.
3. ^ "American Museum of Natural History, Spectacular Stibnite". American Museum of Natural History. http://www.amnh.org/science/papers/stibnite.php. Retrieved on 2007-05-27. 
4. ^ "Chinese stibnite crystal on display in US". http://www.cctv.com/program/cultureexpress/20070406/100505.shtml. Retrieved on 2009-06-06. 
5. ^ P. C. Rickwood (1981). "The largest crystals". American Mineralogist 66: 885-907. http://www.minsocam.org/ammin/AM66/AM66_885.pdf. 

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