Sulides

Sulfides are chemical compounds in which sulfur is bonded to a more electropositive element. In mineralogy, sulfide minerals consist of metal cations bonded to sulfide (S2−) units, forming a wide range of formulas such as MS, MxSy, or more complex compositions.

Sulfides vary widely in appearance and properties, but most have a metallic luster and relatively high density; hardness ranges from soft to fairly hard, depending on composition. Many sulfides are insoluble in water but may react with acids. The bonding in sulfides spans a range from ionic to covalent, and some minerals contain complex polysulfide groups.

Important sulfide minerals include galena (PbS), sphalerite (ZnS), pyrite (FeS2), chalcopyrite (CuFeS2), and bornite (Cu5FeS4). Simple sulfides such as ZnS and CdS occur as well, along with polysulfide minerals such as Sb2S3 and HgS. These minerals are key ore sources for several metals and are widely represented in various ore deposits.

Sulfides form under reducing conditions, commonly in hydrothermal ore deposits, as well as in magmatic and metamorphic environments. They are major sources of metals such as copper, lead, and zinc. Weathering and oxidation of sulfide-rich rocks can produce acid mine drainage, an environmental concern associated with sulfide mineralization.

Industrially, sulfides supply many metals and have applications in pigments, optics, and electronics. Zinc sulfide and cadmium sulfide, for example, have historical and ongoing roles in semiconductor and phosphor technologies. In geology and mining, sulfides are central to studies of ore genesis and environmental impact.