Copper is widely distributed in many parts of the world - mainly as mineral combinations with iron, sulfur, carbon and oxygen. More than 160 copper minerals have been identified, but only about a dozen are commercially important.
Copper minerals are conveniently divided into three groups. Primary or hypogene minerals, which are deposits at considerable depth in the earth by processes related to igneous activity, are represented by compounds such as bornite (Cu5FeS4), chalcopyrite (CuFeS2), enargite (Cu3As5S4) and similar combinations. The second group is composed of oxidized copper minerals, which are commonly formed by the weathering of copper sulfides exposed to erosion. Cuprite (Cu2O), malachite (CuCO3.Cu(OH)2), azurite (2CuCO3.Cu(OH)2) and chrysocolla (CuSiO3.2H2O) are the principal representatives of this group. The third group is that of the secondary sulfides which generally have been formed by copper leached from sulfides exposed near the earth's surface. Chalcocite (Cu2S) and covellite (CuS) are members of this group.
The commercially more important minerals are chalcocite (with 79,8% of copper) and chalcopyrite (with 34,5% of copper). Minerals like enargite and other sulfides are usually extracted in open pits. The deep mining is less common, in copper extraction, due to its high costs.