Chromite is an iron chromium oxide: FeCr2O4. It is an oxide mineral belonging to the spinelgroup. Magnesium can substitute for iron in variable amounts as it forms a solid solution withmagnesiochromite (MgCr2O4); substitution of aluminium occurs leading to hercynite(FeAl2O4).
Chromite is found in peridotite from the Earth's mantle. It also occurs in layered ultramaficintrusive 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 witholivine, magnetite, serpentine, and corundum.
Polymorphism & Series: Forms series with magnesiochromite and hercynite.
Mineral Group: Spinel group.
Occurrence: A cumulus mineral in ultramafic portions of layered mafic igneous rocks; an accessory mineral in alpine-type peridotites; also detrital. Common in all meteorites, except carbonaceous chondrites, and in lunar mare basalts.
Association: Olivine, enstatite, plagioclase, serpentine, magnetite, ilmenite, pyrrhotite, pentlandite, ulvospinel
In Pakistan, chromite is mined from the ultramafic rocks in mainly the Muslim Bagh area of Zhob District of Balochistan. Most of the chromite is of metallurgical grade with Cr2O3 averaging 40% and a chrome to iron ratio of 2.6:1.
Recently, the biggest user of chromite ore has been China, importing large quantities from South Africa, Pakistan and other countries.
Chromite is an oxide mineral composed of chromium, iron and oxygen (FeCr2O4). It is a dark gray to black in color with a metallic to submetallic luster and a high specific gravity. It occurs in basic and ultrabasic igneous rocks and in the metamorphic and sedimentary rocks that are produced when chromite-bearing rocks are altered by heat or weathering.
Chromite And Its Uses
Chromium is a metal used to induce hardness, toughness and chemical resistance in steel. The alloy produced is known as "stainless steel." When alloyed with iron and nickel, it produces an alloy known as "nichrome" which is resistant to high temperatures and used to make heating units, ovens and other appliances. Thin coatings of chromium alloys are used as platings on auto parts, appliances and other products. These are given the name "chrome plated." It is also used to make superalloys that can perform well in the hot, corrosive, and high-stress environment of jet engines.
Chromium's name comes from the Greek word "chroma" which means "color." Chromium is used as a pigment in paint. The familiar yellow lines painted down the center of highways and the yellow paint used on school buses are often "chrome yellow" - a color produced from chromium pigment. Chromium is an important pigment in many types of paint, ink, dye and cosmetics. Trace amounts of chromium produce the color in many minerals and gemstones. The red color of ruby, the pink of some sapphires and the green color of emerald are caused by tiny amounts of chromium.