Pyrite (Drusy) on metal stand from Sukabumi West Java, Indonesia.

Pyrite or iron molar 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) crystals in the shape of a cube with characteristic striations and with a goldish luster. It is also called tinsel or fool's gold (from the English fool's gold) because it was sometimes mistaken for gold. The name cat's gold is sometimes used incorrectly, but this refers to yellow mica or resin. Because pyrite is abundant, 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 sulphurous 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 environment in a t2g6 low spin state. Due to the fact that both ions have a closed configuration, it is a diamagnetic semiconductor. The weathering of pyrite produces iron (hydr)oxides, which also release sulfuric acid. This acid can then react with other minerals and therefore lead to the formation of, for example, gypsum, alunite and jarosite. An important site of pyrite is the island of Elba. The name pyrite is very old, derived from the old Indo-European word pyr (fire, cf. pyrotechnics for fireworks art, or the English pyre (funeral pyre), because sparks could be made by striking pyrite against flint or iron. Today Nowadays we understand flint to be something completely different (a certain form of SiO2). Other names that one may encounter for pyrite are ferrous sulfide, sulfuric iron and the less common words ironblende and ironstone. Pyrite used to be sold for fake gold because it shines gold-like. However, the shine changes when the shining surface tilts, with gold the gold shine remains the same. Pyrite is also angular, with sharp edges and hard, while gold is round and soft.