Alloclasite

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Alloclasite
General
Category Minerals
Formula (Co,Fe)As S
IMA symbol All
Identification
ColorSteel gray to silver
Fracture Irregular/Uneven, Sub-Conchoidal
Mohs scale hardness5
Luster Metallic
Streak Nearly black
Diaphaneity Opaque
Specific gravity 5.95

Alloclasite, or (Co,Fe)As S , is a sulfosalt mineral (IMA symbol: Acl). [1] It is a member of the arsenopyrite group. Alloclasite crystallizes in the monoclinic system and typically forms as columnar to radiating acicular prismatic clusters. It is an opaque steel-gray to silver-white, with a metallic luster and a black streak. It is brittle with perfect cleavage, a Mohs hardness of 5 and a specific gravity of 5.91–5.95. [2]

It was first described in 1866 for an occurrence in Romania. [3] Its name is derived from Greek for "other" and "to break," in reference to its distinct cleavage which distinguished it from the similar appearing mineral marcasite. [4] [2]

The mineral is monoclinic in the P21 space group. [5]

References

  1. ↑ Warr, L.N. (2021). "IMA-CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. 1 2 http://rruff.geo.arizona.edu/doclib/hom/alloclasite.pdf Handbook of Mineralogy
  3. ↑ http://www.mindat.org/min-134.html Mindat data
  4. ↑ http://www.webmineral.com/data/Alloclasite.shtml Webmineral data
  5. ↑ Scott, J.D.; Nowacki, W. (1976). "The crystal structure of alloclasite, CoAsS, and the alloclasite-cobaltite transformation". The Canadian Mineralogist. 14: 561–566.


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