Description
Pyrite, or iron pyrite, is a mineral with the formula FeS2 (chemical name: iron disulfide). The mineral is an important iron and sulfur ore. It often forms well-formed (euhedral) cube-shaped crystals with characteristic striations and a golden luster. It is also called fool's gold because it was sometimes mistaken for gold. The name cat's gold is also sometimes used incorrectly; however, this refers to yellow mica or resin. Because pyrite occurs in abundance, it can create the illusion of great wealth. However, pyrite is not worth very much (although it can be sold). It is found together with other sulfur-containing minerals, but also with oxides, in quartz veins, in sedimentary rocks in coal beds, and as a replacement mineral in fossils. Pyrite is a disulfide with sulfur pairs (S2)2- and Fe2+ ions in an octahedral setting in a t2g6 low spin state. Due to the fact that both ions possess a closed configuration, it is a diamagnetic semiconductor. During the weathering of pyrite, iron (hydr)oxides are formed, releasing sulfuric acid as well. This acid can then react with other minerals, thereby leading to the formation of, for example, gypsum, alunite, and jarosite. An important source of pyrite is the island of Elba. The name pyrite is very old, derived from the ancient Indo-European word pyr (fire, cf. for example pyrotechnics for the art of fireworks, or the English pyre), because sparks could be produced by striking pyrite against flint or iron. Today, we understand flint to mean something quite different (a specific form of SiO2). Other names one may encounter for pyrite are ferrous sulfide, iron sulfide, and the less common words iron blende and pyrites. Pyrite was formerly sold as fake gold because it has a golden luster. However, the luster changes when the surface tilts; with gold, the golden luster remains the same. Pyrite is also angular, with sharp edges, and hard, whereas gold is round and soft.
Pyrite
