Chromite

Chromite, only ore mineral of chromium, consisting of ferrous chromite, FeCr₂O₄, and belonging to the spinel group. It crystallizes in the isometric system (see Crystal) and has a hardness of 5.5 and a specific gravity, or relative density, of 4.1 to 4.8. It is found in irregular brownish-black or black grains or octahedral crystals. Chromite is one of the first minerals to crystallize from magma. It occurs principally in rocks containing various amounts of ferromagnetic minerals. It also occurs in the minerals serpentine and peridotite, as well as in glacial and alluvian deposits (see Alluvium). Deposits of chromite have been found in Kazakhstan, Turkey, India, and South Africa.