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Chromite



Chromite

General
CategoryMineral
Chemical formulairon magnesium chromium oxide: (Fe, Mg)Cr2O4
Identification
ColorBlack to brownish black
Crystal habitOctahedral rare; massive to granular
Crystal systemIsometric; hexoctahedral
Cleavageabsent
FractureConchoidal
Mohs Scale hardness5.5
LusterSubmetallic
Refractive indexSubtranslucent to opaque
StreakDark brown
Specific gravity4.5 - 4.8
FusibilityInfusible
Other CharacteristicsWeakly magnetic
Major varieties
Magnesiochromite

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.

Additional recommended knowledge

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.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chromite". A list of authors is available in Wikipedia.
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