Alloclasite, or (Co,Fe)AsS, 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]
| Alloclasite | |
|---|---|
| General | |
| Category | Mineral |
| Formula (repeating unit) | (Co,Fe)AsS |
| IMA symbol | All |
| Identification | |
| Color | Steel gray to silver |
| Fracture | Irregular/Uneven, Sub-Conchoidal |
| Mohs scale hardness | 5 |
| Luster | Metallic |
| Streak | Nearly black |
| Diaphaneity | Opaque |
| Specific gravity | 5.95 |
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
edit- ^ 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.
- ^ a b http://rruff.geo.arizona.edu/doclib/hom/alloclasite.pdf Handbook of Mineralogy
- ^ http://www.mindat.org/min-134.html Mindat data
- ^ http://www.webmineral.com/data/Alloclasite.shtml Webmineral data
- ^ 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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