chromite

Chromite is the mineral and primary ore of chromium. Its ideal formula is FeCr2O4, but iron and chromium contents vary within the spinel structure. In chromite, Fe2+ is in tetrahedral sites and Cr3+ in octahedral sites, with substitutions by Mg2+, Al3+, and other cations. It is typically dark brown to black, with a metallic to submetallic luster, relatively high density, and a hardness of about 5.5–6 on the Mohs scale.

Chromite occurs mainly in ultramafic and mafic rocks, especially peridotites and dunites, and in chromitite layers within layered intrusions such as the Bushveld Complex. It forms by crystallization of basaltic magma and by later alteration that concentrates chromium. Chromite grains can be disseminated or concentrated in thick seams.

As the primary source of chromium, it is processed into ferrochromium alloys for stainless steel production and into chromium metal. Chromium is also used for electroplating, refractories, and pigments. Beneficiation typically involves crushing, grinding, and magnetic separation to produce concentrate, which is then smelted or refined.

Global production centers include South Africa, Kazakhstan, India, Turkey, Finland, and Russia, with important deposits in Oman, Albania, and Zimbabwe. Mining and processing raise concerns about dust, emissions, and chromium compound exposure, prompting regulatory controls in many countries.