Covellite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameCovellite
Chemical FormulaCuS
Mohs Hardness1.5
Crystal Systemhexagonal
Lustervitreous
Streak Colorgray to black
Cleavageperfect on {0001}
Fractureuneven
Specific Gravity4.6
Colorsindigo blue, dark blue, purplish-black
Transparencyopaque
Type LocalityEast Colusa Mine, Butte, Butte District, Silver Bow County, Montana, USA
Mineral GroupSulfides
Usesminor copper ore, collector's mineral
Associated Mineralschalcocite, bornite, chalcopyrite, pyrite
Rarityuncommon
Description
This specimen features deep indigo blue to purplish-black covellite crystals, often exhibiting a striking iridescent tarnish. The crystals typically form platy or tabular aggregates.
Geological Context
Covellite is a secondary mineral found in the supergene enrichment zones of copper sulfide deposits, often forming from the alteration of primary copper sulfides. It can also occur in hydrothermal veins.
