Chromite is an iron-chromium oxide: FeCr2O4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts, as it is a solid solution with magnesiochromite (MgCr2O4) forms; substitution of aluminum occurs, leading to hercynite (FeAl2O4).
Chromite deposits
Chromite is found in peridotite from the mantle. It also occurs in layered ultramafic intrusive rocks. Furthermore, it is found in metamorphic rocks such as some serpentinites. Ore deposits of chromite form as early magmatic differentiates. It is generally associated with olivine, magnetite, serpentine, are connected, and corundum. The vast Bushveld igneous complex of South Africa is a large layered mafic to ultramafic igneous body with some layers consisting of 90% chromite making the rare rock type, chromitite. The Stillwater igneous complex in Montana also contains significant chromite. Read the rest of this entry »