Stibnite

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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
Cleavage	Perfect
Fracture	Small-scale subconchoidal
Mohs Scale hardness	2
Luster	Splendent on fresh crystals surfaces, otherwise metallic
Refractive index	Opaque
Streak	Similar to color
Specific gravity	4.56 - 4.62
Solubility	decomposed with hydrochloric acid
Major varieties
Metastibnite	Earthy, reddish deposits

Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb₂S₃. It forms grey orthorhombic crystals of hardness 2. It is the most important source for the rare metaloid antimony.

1 Formation and structure
2 Uses
3 Occurrence
4 See also
5 References
6 External links

[edit] Formation and structure

Stibnite is formed from antimony(III) compounds 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.^[1] Related reactions were once used in university courses on qualitative inorganic analysis.

Stibnite has a structure similar to that of As₂S₃. The Sb(III) centers, which are pyramidal and three-coordinate, are linked via bent two-coordinate sulfide ions.

[edit] Uses

Stibnite is used to make fireworks, metal antifriction alloys, and batteries.^[2] It was used as mascara by Queen Jezebel of the Old Testament (2 Kings 9,30) and is an ingredient of safety matches.^{[citation needed]}

[edit] Occurrence

Small deposits of stibnite are common; 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. Large iridescent stibnite crystals are found in Japan.^{[citation needed]}

Stibnite specimen at the American Museum of Natural History

As of May 2007, the largest specimen on public display (1000 pounds) is at the American Museum of Natural History.^[3]

[edit] See also

List of minerals

[edit] References

^ 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.
^ Mineral Information Institute, Antimony. Mineral Information Institute. Retrieved on 2007-05-27.
^ American Museum of Natural History, Spectacular Stibnite. American Museum of Natural History. Retrieved on 2007-05-27.