pyrite (fool's gold) Sulphide mineral, FeS₂; sp. gr. 4.9–5.2; hardness 6.0–6.5; cubic; pale brass-yellow, does not tarnish; greenish-black streak; metallic lustre; crystals cubic, pyritohedra (pentagonal dodecahedra), octahedra, or combinations of the two; cleavage poor basal hardness; occurs with other sulphide ores genetically associated with basic and ultrabasic rocks, and together with pyrrhotine and chalcopyrite; very widely distributed in a great variety of environments, and found in igneous rocks as an accessory mineral, in sedimentary rocks (especially black shales), as nodules in metamorphic rocks, and common in hydrothermal veins, in replacement deposits, and contact metamorphic rocks; alters to iron sulphate and limonite. It was formerly used widely for the production of sulphuric acid. Compare MARCASITE.

py·rite / ˈpīˌrīt/ (also py·ri·tes / pəˈrītēz; pī-/ ) • n. a shiny yellow mineral consisting of iron disulfide and typically occurring as intersecting cubic crystals; compare with marcasite. Also called fool's gold.DERIVATIVES: py·rit·ic / pīˈritik; pə-/ adj.py·rit·i·za·tion / pəˌrītəˈzāshən; pī-/ n.py·ri·tize / ˈpīrītˌīz/ v.py·ri·tous / pəˈrītəs; pī-/ adj.

pyrite (fool's gold) Widespread sulphide mineral, iron sulphide (FeS₂), occurring in all types of rocks and veins. It is a brass-yellow colour. It crystallizes as cubes and octahedra, and also as granules and globular masses. It is opaque, metallic, and brittle. Hardness 6.5; r.d. 5.0.