sulfiidit

Sulfiidit are a broad class of chemical compounds in which sulfur is bonded to a metal or semimetal with sulfur in the −2 oxidation state. In geology and mineralogy they refer especially to mineral species whose dominant anion is S2−, forming a range of binary and complex sulfide minerals. Common examples include pyrite (FeS2), galena (PbS), sphalerite (ZnS), chalcopyrite (CuFeS2), and pyrrhotite (Fe1−xS). Other notable sulfiidit minerals are marcasite, arsenopyrite (FeAsS), and stibnite (Sb2S3).

These minerals form in several geological settings: hydrothermal ore veins associated with magmatic activity, high-temperature metasomatism, magmatic differentiation, and sedimentary diagenesis. Pyrite is among the most common sulfide minerals and occurs in virtually all rock types; sphalerite and galena are important contributors to ore deposits; chalcopyrite is a major source of copper. Sulfiidit can also occur as secondary minerals formed during weathering and alteration.

Properties and chemistry: sulfide minerals typically have metallic luster, high density, and a tendency to fracture. They are often opaque and electrically conductive; many are brittle. Most sulfide minerals are stable in reducing environments but oxidize upon exposure to air and water, a process that can produce sulfuric acid and metal sulfates in environments such as mine drainage. Some sulfiidit also form complex sulfide phases with variable compositions and mixed anion groups.

Industrial and environmental aspects: sulfiidit minerals are economically important as ore sources for metals including iron, copper, zinc, lead, nickel, and cobalt. Ore processing usually involves roasting and smelting to separate metal from sulfur. Some sulfide minerals have applications in optics and electronics as semiconductor or luminescent materials. Environmentally, sulfide oxidation can release H2S gas and acidifying drainage, necessitating mitigation in mining and processing operations.