Cobaltite

Cobaltite is a sulfide mineral composed of cobalt, arsenic, and sulfur, CoAsS. Its impurities may contain up to 10% iron and variable amounts of nickel.[5] Structurally, it resembles pyrite (FeS2) with one of the sulfur atoms replaced by an arsenic atom.

Cobaltite
Cobaltite from Sweden
General
CategorySulfide mineral
Formula
(repeating unit)		CoAsS
Strunz classification2.EB.25
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
(same H-M symbol)
Space groupPc21b
Unit cella = 5.582 Å,
b = 5.582 Å,
c = 5.582 Å; Z = 4
Identification
ColorReddish silver white, violet steel gray to black
Crystal habitGranular to massive, rarely as striated crystals, pseudocubic.
TwinningAbout [111] creating pseudo-cubic forms and striations
CleavagePerfect on {001}
FractureUneven
TenacityBrittle
Mohs scale hardness5.5
LusterMetallic
StreakGrayish-black
DiaphaneityOpaque
Density6.33 g/cm3
References[1][2][3][4]

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 as they are expected to.[6]

It occurs in high-temperature hydrothermal deposits and contact metamorphic rocks. It occurs in association with magnetite, sphalerite, chalcopyrite, skutterudite, allanite, zoisite, scapolite, titanite, and calcite along with numerous other Co–Ni sulfides and arsenides.[2] It was described as early as 1832.[3]

It is found chiefly in Sweden, Norway, Germany, Cornwall, England, Canada, La Cobaltera, Chile, Australia, the Democratic Republic of the Congo, and Morocco.[2][5][4]

Cobaltite can be separated from other minerals by selective, pH controlled, flotation methods, where cobalt recovery usually involves hydrometallurgy. It can also be processed with pyrometallurgical methods, such as flash smelting.[7]

References
  1. Mineralienatlas
  2. http://rruff.geo.arizona.edu/doclib/hom/cobaltite.pdf Mineral Handbook
  3. http://webmineral.com/data/Cobaltite.shtml Webmineral data
  4. https://www.corfo.cl/sites/Satellite?blobcol=urldata&blobkey=id&blobtable=MungoBlobs&blobwhere=1475166619420&ssbinary=true Corfo Report
  5. Klein, Cornelus and Cornrlius Hurlbut, 1996, Manual of Mineralogy, 20th ed., Wiley, p.288, ISBN 0-471-80580-7
  6. http://www.mindat.org/min-1093.html Mindat
  7. "Copper-Cobalt ores". www.danafloat.com. Retrieved 2018-04-04.
Cubic Cobaltite, 1.6 x 1.4 x 1.1 cm, Brazil Lake Occurrence (Elizabeth Lake Mine), Sudbury District, Ontario, Canada
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