Pyrite

Definition

Pyrite is an iron sulfide with the formula FeS₂. It has a metallic luster and a pale yellow color (hence the name “fool’s gold”). It is relatively hard and commonly forms cubic crystals. It is the most common sulfide mineral and forms under a wide variety of conditions: in relatively oxidized magmas, from hydrothermal fluids, in metamorphic rocks, and in sediments. It is rarely a primary mineral in high-temperature rocks, and usually forms by replacement of high-temperature minerals under oxidizing conditions. It is also a common mineral in many types of sulfide ore and is present in most gold deposits. It grows or recrystallizes during the diagenesis of sediments, commonly through the action of bacteria: framboidal pyrite in sediments is commonly biogenic. Oxidation of pyrite provides an energy source for microbes in anaerobic settings. It is an important mineral for understanding the redox changes at the surface of the Earth, particularly during the Great Oxygenation Event...