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Home > Products > Minerals > Chromate

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What Is Chromate?

Commonly found in meteorites and metamorphic rocks such as serpentites 
Name: Chromite
Chemistry: FeCr2O4
Color: Deep dark black, brownish black 
Hardness: 5.5
Specific Gravity: 4.5-4.8
Crystals: Isometric
Accompanied by: Anorthite, Biotite, Magnetite, Magnesium, Olivine, Serpentine, Talc, Uvarovite, Pyroxenes
Fracture: Uneven / conchoidal
Luster: Metallic to greasy
Cleavage: None
Used in a wide range of industrial process. Natural Chromite contains some magnesium. It is weakly magnetic and an octahedral parting is sometimes seen
• Chemical Formula: FeCr2O4, Iron Chromium Oxide. 
• Class: Oxides and Hydroxides 
• Group: Spinel 
• Uses: The principle ore of chromium, as a refractory component, as a dye and as mineral specimens. 
• Specimens 
Chromite is the most important ore of chromium from which it derives its name. Chromium is an important metal and has a wide range of industrial uses. 
Chromite forms in deep ultra-mafic magmas and is one of the first minerals to crystallize. It is because of this fact that Chromite is found in some concentrated ore bodies. While the magma is slowly cooling inside the Earth's crust, chromite crsytals are forming and because of their density, fall to the bottom and are concentrated there. 
Although its primary origin is ultra-mafic rocks such as peridotites, Chromite is also found in metamorphic rocks such as serpentites. Chromite, as is indicated by its early crystallization is resistant to the altering affects of high temperatures and pressures. Thus it is capable of going through the metamorphic processes unscathed, while other minerals around it are being altered to serpentine, biotite and garnets. This characteristic also explains chromites use as a refractory component in the bricks and linings of blast furnaces. 
Usually magnesium is present in Chromite substituting for the iron and in fact a solid solution series exists between Chromite and the much rarer mineral magnesiochromite. All Chromite specimens in nature contain some magnesium; likewise all natural magnesiochromites contain some iron. Magnesiochromite is grayer in color and in streak and has a slightly lower density than chromite at a specific gravity of 4.2 to 4.4.

Chromite Packing

All grades of Chromite are available in various types of packaging:
1. 1 Ton Jumbo bags
2. 25kg package for powder

Chromate Physical Properties

Cell Dimensions: a = 8.36, Z = 8; V = 584.28 Den(Calc)= 5.09 
Crystal System: Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: F d3m 
X Ray Diffraction: By Intensity (I/Io): 2.52(1), 1.46(0.9), 1.6(0.9).

Chromate Physical Properties

 

Hardness

5.5

Specific gravity

4.5 - 4.8 (average for metallic minerals)

Color

Brownish black to a deep dark black

Crystal Habits

Include octahedrons often with dodecahedral faces modifing the edges of the octahedron to the point of rounding the crystal. Well formed crystals are rare and chromite is usually found massive or granular.

Luster

Metallic to greasy

Streak

Brown

Transparency

Crystals are opaque

Crystal System

Isometric; 4/m bar 3 2/m

Cleavage

Absent

Fracture

Conchoidal

Other Characteristics

Weakly magnetic and an octahedral parting is sometimes seen.

Associated Minerals

Include olivine, talc, serpentine, uvarovite, pyroxenes, biotite, magnetite and anorthite.

Best Field Indicators

Crystal habit, streak, associations with ultra-basic minerals and parting.