About 500 minerals belong to the sulfides and related minerals, and most consist of metal and semimetal sulfides such as pyrite (FeS2), chalcopyrite (CuFeS2), and sphalerite (ZnS). Sulfides are generally subdivided into three chemical classes: (a) simple sulfides that are salts of HS (e.g., sphalerite, ZnS is the zinc salt of HS); (b) salts of thioacids, which are oxygen-free acids with sulfur playing the role of oxygen (e.g., pyrargyrite, Ag3SbS3 is the silver salt of the sulfoacid H3SbS3), and (c) polysulfuric compounds (persulfides) that can be considered as salts of the polysulfuric acid H2S2, which contains the bivalent S22- molecule (pyrite is an example). The closest analog to sulfides are arsenides and their complex compounds (arsenide–sulfides) such as realgar (FeAs2) and arsenopyrite (FeAsS), with structures similar to that of pyrite.
Sulfides are of great industrial importance and are the major ores for copper, zinc, lead, mercury, bismuth, cobalt, nickel, and other nonferrous metals. (Ferrous metals such as iron, chromium and manganese are not extracted from sulfides, because sulfur interferes with the metal recovery process.) Sulfides are also the sources of arsenic and antimony. Although pyrite is not an ore for iron, it is used to produce sulfuric acid and it is also an important gold ore, containing small fragments of native gold as inclusions.
The structural properties of sulfides are determined by bonding between a metal and sulfur, which is highly ionizing.