Chromite

Chromite, iron magnesium chromium oxide: (Fe, Mg)Cr₂O₄, is an oxide mineral belonging to the spinel group. Magnesium is always present in variable amounts, also aluminium and iron substitute for chromium.

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Chromite is found in peridotite and other layered ultramafic intrusive rocks and also found in metamorphic rocks such as serpentinites. Ore deposits of chromite form as early magmatic differentiates. It is commonly associated with olivine, magnetite, serpentine, 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.

Chromite is also used as a refractory material.  

The only ore of chromium is the mineral chromite. In the western hemisphere, chromite ore is produced only in Brazil and Cuba; By comparison, about 80% of world production of chromite comes from India, Iran, Pakistan, Oman, Zimbabwe, Turkey and Southern Africa. Southern Africa itself produces about half of this.

Chromite is mined from the ultramafic rocks in the Zhob District of Balochistan. Most of the chromite is of metallurgical grade with Cr₂O₃ averaging 46% and a chrome to iron ratio of 3:1.

References

• Dana's Manual of Mineralogy ISBN 0-471-03288-3
• Guilbert, John M., and Park, Charles F., Jr. (1986) The Geology of Ore Deposits, Freeman, ISBN 0-7167-1456-6
• Mineral Galleries: Chromite
• Webmineral.com
• Minerals.net
• USGS info.