Chromium

chromium

danbaite

pentlandite

diamond

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Formula: Cr
Native element, transition metal
Specific gravity: 7.17
Hardness: 9
Colour: White
Melting point: 1907oC
Boiling point: 2670oC
Environments

Metamorphic environments

Chromium is seldom found in the native state. The main ore is chromite. Abundance in the Earth’s crust is 102 parts per million by mass, 40 parts per million by moles, and abundance in the Solar System is 20 parts per million by mass, 0.4 parts per million by moles (ChC).

Localities

In Liaoning Province,China, native chromium has been found in a kimberlite pipe (HOM).

At the Yangliuping Cu-Ni-PGE deposit, Danba county, Garzê Autonomous Prefecture, Sichuan, China, native chromium has been found in heavy sands derived from the contact metamorphic zone between a siliceous marble and ultramafic rock. it is finely granular with grain size about 20 pm, and closely associated with danbaite, which forms rims around chromium. Other associated minerals include pyrrhotite, pentlandite, chalcopyrite, pyrite, sulpharsenides and platinum group minerals (AM 67.854-855, HOM).

At the type locality, the Anduo Cr deposit, Amdo county, Nagchu Prefecture, Tibet, China, native chromium is found in Heavy sands derived from a contact metamorphic zone between siliceous marble and ultramafic rock (Mindat, Webmin).

At the Luobusha ophiolite, Qusum county, Shannan Prefecture, Tibet, China, native chromium is found in podiform chromitites (HOM).

At the Gavasai ore field, Chatkal district, Jalal-Abad Region, Kyrgyzstan, native chromium is found in ultramafic dike rocks with cohenite, moissanite, ilmenite and titanite (HOM).

In the Far-Eastern Economic Region, Russia, native chromium is found in in serpentinite in duniteperidotite (HOM).

At the Udachnaya open-pit mine, Daldyn, Mirninsky District, Sakha Republic, Russia, native chromium is found in kimberlite as inclusions in diamonds (HOM, Dana).

Chromium-bearing minerals include:

Sulphides
daubréelite

Oxides
crichtonite
davidite-(Ce)
davidite-(La)
eskolaite
hemleyite
magnesiochromite

Chromates
chromatite
crocoite
hemihedrite
iranite
phoenicochroite

Phosphates
vauquelinite

Arsenates
fornacite

Nesosilicates
uvarovite

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