Enargite

minerals

hydrothermal

pyrite

Formula: Cu3AsS4
Sulphosalt
Specific gravity: 4.4
Hardness: 3½
Streak: Black
Colour: Steel grey to iron black
Solubility: Slightly soluble in nitric acid
Common impurities: Sb,Fe,Pb,Zn,Ag,Ge
Environments:

Hydrothermal environments

Enargite is a comparatively rare mineral, found in vein and replacement deposits formed at moderate temperatures associated with pyrite, sphalerite, bornite, galena, tetrahedrite, covellite and chalcocite. Enargite occurs in arsenic containing copper ore veins.

At the Gregory mine, Ashover, Derbyshire, England, UK, enargite has been found with calcite (RES p103).

Alteration

enargite and pyrite to Fe-tennantite, chalcopyrite and sulphur
4Cu3AsS4 + 4FeS2 → Cu10Fe2As4S13 + 2CuFeS2 + 7/2S2
(CM 28.725-738)

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