Chromite


MINERAL : CHROMITE

Chromite is an iron chromium oxide FeCr2O4 and the lone ore of chromium metal. It has wide range of chemical composition which depends on kind of deposits it is occurring in. Generally the content of chromium is more compared to iron which may be in the ratio of 2:3 to 2:4. Some times magnesium replaces the iron making it as magnesiochromite. There also some amount of compounds like platinum, vanadium, cobalt and nickel present in it. Its one of the high content mineral. In the 20th century, the use of chromium exploded due to the industrialization and surge in demand for stainless steel.

Chromium usage can be divided into 3 categories:

Metallurgy-90%, Chemical : 5%, Refractory and Foundry : 5%
In some case the chromium oxide and aluminium oxide content which 2/3 rd of the total composition.And also silica content should be less than 6% in it. Iron oxide should be low i.e to 20%. The mineral is found not only as crystals embedded in the rock mass, but also as nodules in it and as veins traversing it. One of the first minerals to separate from a cooling rock magma, and its large ore deposits are thought to have been derived by such magmatic differentiation.

OCCURENCE AND DEPOSITS

Chromite forms in deep ultra-mafic magmas and is one of the first minerals to crystallize. It is also found in peridotite from the Earth's mantle. 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. Large commercial deposits exist in Russia, India, Kazakstan, Philippines, New Caledonia, former Yugoslavia, Zimbabwe, Turkey, Brazil, and Cuba. In recent days the biggest user of chromite ore has been China. In the U.S., Chromite has come from the Bare Hills, near Baltimore, Maryland, and the Wood's Mine, near Texas. South Africa is the largest producer of chromite ores, where over 70% of world chromite ore reserves are believed to be located. Today South Africa supplies approximately 50% of world's supplies of chromite ores.

Hatton FZE operates one of the largest chromite quarry in Somail area, south of Muscat, Oman. The chromite ores are of various grades and ranges from 30% to 42%. The production capacity is 2,000 MT per day or 40,000 MT per month or 480,000 MT per year. Since Oman is a desert and almost never rains, production can continue year round. In India chromite is found in Orissa as dissemination, veins, and lensoid within the ultrabasic rocks. In Karnataka and Maharashtra it is found in veins and lensoid form.

PROPERTIES
1. Colour of chromite varies from brownish black to greenish black.
2. It has a metallic lustre with brown streak.
3. Its a brittle mineral with opaque structure.
4. It is hard mineral with 5.5 to 6 hardness on Mohs scale.
5. Specific gravity is around 4.5 to 5.
6. Chromite is weekly magnetic.
7. Its density is 5.12 g/cm3.
8. Cleavage is absent in chromite


APPLICATIONS OR USES
1. Chromites are used as a refractory component in the bricks and linings of blast furnaces.
2. Chromium is also used for the manufacture of ferrochromium and metallic chromium.
3. Also used in steel industries to improve its hardness, and chemical composition.
4. When mixed with nickel it forms nichrome which can be used in industries operating at high temperatures.
5. Thin coatings of chromium alloys are used as platings on auto parts, appliances and other products and given the name chrome plated. 6. Chromium salts are used in tanning and as pigments and plating.
7. Chromite is used in chemical industries for the manufacture of sodium dichromate, potassium dichromate, ammonium dichromate, chromium nitrate and chromic acid etc.

Question and Answers

1. What is the chemical formula of chromite?
Ans : Chemical formula of chromite is FeCr2O4.
2. Who is the major consumer of chromite mineral?
Ans : China is the major consumer of chromite mineral.
3. What are the properties of chromite?
Ans : a. Its a brittle mineral with opaque structure. b. It is hard mineral with 5.5 to 6 hardness on Mohs scale. c. Specific gravity is around 4.5 to 5.
4. Mention few applications of chromite?
Ans : a. Chromites are used as a refractory component in the bricks and linings of blast furnaces.
b. Thin coatings of chromium alloys are used as platings on auto parts,appliances and other products and given the name chrome plated.

References :
1. www.wikipedia.com
2. www.galleries.com
3. www.mineralzone.com

More pages