Minerals (Category A)
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 forms a solid solution with magnesiochromite (MgCr2O4); substitution of aluminium occurs leading to hercynite (FeAl2O4).
It is by far the most industrially important mineral for the production of metallic chromium, used as an alloying ingredient in stainless and tool steels.