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Mineralpedia Details for Chromite

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Chromite

Chromite

Named for the content of chromium. Chromite is a common and widespread mineral that occurs in the ultramafic layers of layered igneous intrusions, as an accessory mineral in Alpine-type peridotites, as a detrital mineral, in meteorites, and in lunar basalts. Large crystals can be found in France, Sierra Leone, and New Caledonia, and economic deposits are found at the Bushveld complex in South Africa, the Great Dyke in Zimbabwe, localities in Turkey, in the Ural Mountains in Russia, from the Moa district in Cuba, on Luzon in the Philippines, and from the Stillwater complex in Montana, USA. Many other localities are known. Occasionally, some samples of Chromite are weakly magnetic.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/chromite.pdf

Formula
Fe2+Cr2O4 
Crystal System
Isometric 
Crystal Habit
Massive - Granular, Granular, Nuggets 
Cleavage
None, None, None 
Luster
Metallic 
Color
black, brownish black 
Streak
brown 
Class
Isometric - Hexoctahedral 
Fracture
Uneven 
Hardness
5.5 
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Chromite from Twamba, Tanzania

Chromite
            from Twamba, Tanzania

Dull black nodular or tube-like structures of Chromite in parallel "growth". 

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Chromite from Stillwater mine, Nye Co., Montana, United States

Chromite
            from Stillwater mine, Nye Co., Montana, United States

Rich, solid granular or crystalline aggregate of black Chromite ore. Though not producing Chromite ore, this large 30 mile complex of layer igneus mafic rock currently does not produce chromium ore. It is currently mined for its platinum and palladium only. Ore specimens are hard to obtain.

Widely used in chemicals, metals and refractory materials. Used to harden iron, nonferrous alloys and steel. The addition of 10% chromium also creates corrosion and oxidation resistant alloys such as stainless steel. According to the USGS Minerals Commodity Summary of 2106, about 95% of the world’s chromium resources is geographically concentrated in Kazakhstan and southern Africa; U.S. chromium resources are mostly in the Stillwater Complex in Montana although not currently producing chromium. 

1 lb 5oz

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Chromite with Clinochlore from Brush Creek, Green Mtn., Yancey Co., North Carolina, United States

Chromite with Clinochlore
            from Brush Creek, Green Mtn., Yancey Co., North Carolina, United States

Coarse granular Chromite with purple alterations to chromium Clinochlore.

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