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| Chromite | |
|---|---|
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| General | |
| Category | Mineral |
| Chemical formula | iron magnesium chromium oxide: (Fe, Mg)Cr2O4 |
| Identification | |
| Color | Black to brownish black |
| Crystal habit | Octahedral rare; massive to granular |
| Crystal system | Isometric; hexoctahedral |
| Cleavage | absent |
| Fracture | Conchoidal |
| Mohs Scale hardness | 5.5 |
| Luster | Submetallic |
| Refractive index | Subtranslucent to opaque |
| Streak | Dark brown |
| Specific gravity | 4.5 - 4.8 |
| Fusibility | Infusible |
| Other Characteristics | Weakly magnetic |
| Major varieties | |
| Magnesiochromite | |
Chromite is iron magnesium chromium oxide: (Fe, Mg)Cr2O4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts; also, aluminium and ferric iron commonly substitute for chromium.
Chromite is found in peridotite from the Earth's mantle. It also occurs in layered ultramafic intrusive rocks. In addition, it is found in metamorphic rocks such as some 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.
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Wikipedia content modification information:
- This page was last modified on 17 September 2008, at 03:26.
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