Massive pieces of Chalcocite showing conchoidal fracture. View on the
right is a close-up showing associated chalcopyrite grains.
CHEMISTRY Cu2S Copper sulfide
CRYSTALLOGRAPHY Monoclinic (pseudo orthorhombic)
CRYSTAL GROWTH AND HABITS Chalcocite crystals grow as short prismatic to thick tabular crystals, but most commonly it is compact and massive.
COLOR AND OTHER OPTICAL PROPERTIES Lead gray; opaque
HARDNESS 2.5 - 3
SPECIFIC GRAVITY 5.5 - 5.8
LUSTER Metallic to submetallic
STREAK Dark gray
BREAKABILITY Indistinct cleavage and conchoidal fracture
OCCURRENCE Chalcocite is found as a secondary mineral in copper sulfide ore bodies.
ASSOCIATED MINERALS Pyrite, Chalcopyrite, Covellite, Bornite