Sulfide

Sulfide refers to compounds containing sulfur in the −2 oxidation state. The sulfide ion, S2−, readily forms salts with metal cations, producing many solid compounds. In minerals, sulfides form extensive ore deposits and exhibit varying solubilities and colors.

Common sulfide minerals include pyrite (FeS2), galena (PbS), and sphalerite (ZnS). These minerals are often found in hydrothermal veins and ore deposits and are significant sources of metals such as iron, lead, and zinc. Many sulfides are insoluble in water, but acids can release hydrogen sulfide gas (H2S).

Hydrogen sulfide is a colorless, toxic, flammable gas with a rotten-egg odor at low concentrations; at higher levels, odor detection may be lost. In nature, sulfide occurs in anoxic environments produced by sulfate-reducing bacteria. Industrially, sulfide chemistry is used in pigment production (zinc sulfide ZnS, cadmium sulfide CdS) and in metallurgy and catalysis; sulfides are also encountered as corrosion products and in oil and gas desulfurization processes. Environmental concerns include acid mine drainage, where sulfide minerals oxidize to sulfuric acid, mobilizing metals.