chalcocite, sulfide mineral that is one of the most important ores of copper. Valuable occurrences include deposits of sulfide minerals at Ely, Nev., and Morenci, Ariz., where other components of the original rock have been dissolved away; it is also found with bornite in the sulfide veins of Tsumeb, Namibia, and Butte, Mont. For detailed physical properties, see sulfide mineral (table).
Chalcocite (Cu2S) belongs to a group of sulfide minerals formed at relatively low temperatures (see also argentite). Chalcocite alters to native copper and other copper ores.