Cobaltite
Cobaltite from Sweden
General
Category	Sulfosalt mineral
Chemical formula	CoAsS
Identification
Color	Reddish silver white, violet steel gray to black
Crystal habit	Granular to massive, rarely as striated crystals
Crystal system	Orthorhombic, pseudocubic.
Twinning	About [111] creating pseudo-cubic forms and striations
Cleavage	Good in three directions
Fracture	Brittle
Mohs scale hardness	5.5
Luster	Metallic
Streak	Grayish-black
Specific gravity	6.33
Optical properties	Opaque
Other characteristics	magnetic after heating
References	[1][2]

Cobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel.^[3] Structuraly it resembles pyrite (FeS₂) with one of the sulfur atoms replaced by an arsenic atom.

Although rare it is mined as a significant source of the strategically important metal cobalt. Secondary weathering incrustations of erythrite, hydrated cobalt arsenate, are common.

The name is from the German, Kobold, "underground spirit" in allusion to the refusal of cobaltiferous ores to smelt properly.^[4]

It occurs in high temperature hydrothermal deposits and contact metamorphic rocks. It occurs in association with magnetite, sphalerite, chalcopyrite, skutterudite, allanite, zoisite, scapolite, titanite, calcite along with numerous other Co–Ni sulfides and arsenides.^[1] It was described as early as 1832 and its type locality is Cobalt, Ontario.^[2]

It is found chiefly in Sweden, Norway, Germany, Cornwall, England, Canada, Australia, Democratic Republic of the Congo and Morocco.^[1][3]

[edit] References

1. ^ ^{a b c} http://rruff.geo.arizona.edu/doclib/hom/cobaltite.pdf Mineral Handbook
2. ^ ^{a b} http://webmineral.com/data/Cobaltite.shtml Webmineral data
3. ^ ^{a b} Klein, Cornelus and Cornrlius Hurlbut, 1996, Manual of Mineralogy, 20th ed., Wiley, p.288, ISBN 0-471-80580-7
4. ^ http://www.mindat.org/min-1093.html Mindat

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