chromite (krōˈmĪt) [key], dark brown to black mineral. It is an iron-chromium oxide, FeCr2O4, with traces of magnesium and aluminum. Its crystals are octahedral, but rare; it usually occurs as irregular, granular masses in association with igneous rocks, including ophiolites, which are segments of oceanic crust exposed on land by tectonic processes usually associated with plate convergence (see plate tectonics). Chromitite is an igneous rock composed chiefly of the mineral chromite. The only commercial source of chromium and its compounds, chromite is used in the manufacture of refractory materials. Principal countries producing chromite are South Africa, Zimbabwe, the Philippines, and Turkey.
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