Chromite is the commercial name for iron chromium oxide (FeCr2O4), a mineral containing chromium (a transition metal with multiple oxidation states) and iron oxide. In its purest form, chromite comprises chromium (Cr2O3) at 68% and iron oxide (FeO) at 32%. Chromite occurs exclusively in ultramafic rocks such as dunite, peridotite, pyroxenite and serpentinite. High purity deposits are rare owing to replacement by certain elements. In nature, ferrous iron tends to be partially replaced by magnesium, while chromium may be partially replaced by aluminium or ferric iron.
World chromite reserves are estimated to total around 7.6 bn tonnes, with the majority of this located in South Africa. The country is by far the single largest holder of the world’s chromite reserves, accounting for 5.5 bn tonnes (72%) – much of which is held in the Bushveld Igneous Complex.