Covellite
Image: Islam90 (CC BY-SA 4.0)
Mineral NameCovellite
Chemical FormulaCuS
Mohs Hardness1.5
Crystal Systemhexagonal
Streak Colorlead-gray to black
Cleavageperfect on {0001}
Fractureuneven
Specific Gravity4.6
Colorsindigo-blue, dark blue, purplish-blue
Transparencyopaque
Type LocalityVesuvius, Italy
Mineral GroupSulfides
Usesminor copper ore, collector's mineral
Associated Mineralspyrite, chalcopyrite, bornite, chalcocite
Rarityuncommon
Description
The image displays a microscopic view of a polished section, showing a matrix of bluish-grey covellite with scattered, brighter, and more reflective grains of pyrite. The covellite exhibits its characteristic indigo-blue color under normal light, while pyrite appears as pale brass-yellow to whitish metallic specks.
Geological Context
Covellite is typically a secondary copper sulfide formed in supergene enrichment zones of copper deposits, often replacing primary sulfides like pyrite or chalcopyrite. Pyrite, a common iron sulfide, is frequently found as a primary mineral in such deposits, and its presence here suggests a paragenetic relationship where covellite may have formed at its expense or co-existed.
