Pyrite, or iron pyrite, is an iron sulfide with the chemical formula FeS2. It is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, and the mineral is known informally as "fool's gold". The color has also led to the nicknames brass, brazzle, and Brazil, primarily used to refer to pyrite found in coal. Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds and as a replacement mineral in fossils, but has also been identified in the sclerites of scaly-foot gastropods. It has had various uses over time, including as an ignition for firearms, a source of sulfur dioxide and as jewellery. These cubic crystals of pyrite were found in the Huanzala mine in the Huallanca District of Peru.Photograph credit: Ivar Leidus