pyrrhotite

pyrrhotite or magnetic pyrites, bronze-yellow to bronze-red mineral, a sulfide of iron sometimes containing nickel. It tarnishes easily and is somewhat magnetic. It crystallizes in the hexagonal system, but appears usually in massive form, and occurs chiefly in basic igneous rocks. In some areas, e.g., at Sudbury, Ont., Canada, it is associated with pentlandite, an important ore of nickel. It is found also in the United States, Europe, and South America.

pyrrhotite Mineral, FeS; sp. gr. 4.6–4.7; hardness 3.5–4.5; hexagonal; bronzeyellow but darkens rapidly to reddishbrown on exposure; greyish-black streak; metallic lustre; crystals rare, and can be platy or tabular, but the mineral is usually massive or granular; no cleavage; magnetic; occurs in igneous rocks, e.g. gabbro or norite, as disseminated grains, and also in metamorphic contact zones in association with chalcopyrite and pyrite. Pyrrhotite was used formerly for the production of sulphuric acid.