English: Chalcocite is an important copper mineral ore. It has the composition of Cu2S. The reasons for its importance is its high copper content and the ease at which copper can be separated from sulfur. Chalcocite occurs as a secondary mineral in many ore bodies in a zone called the supergene enrichment zone. Chalcocite commonly forms from the alteration of primary copper minerals that are attacked above the water table by oxygen. Ore bodies will have a layer of chalcocite which corresponds to the present or a past water table level and this layer is called a chalcocite blanket. The chalcocite blanket is richer in copper than the upper oxidized portion of the ore body and usually richer than the primary unaltered ores below.