Chromite is an oxide mineral composed of chromium, iron and oxygen (FeCr2O4). It also can be found as in a composition to magnesium instead of iron and become the magnesiochromite (MgCr2O4).
It is a dark gray to black in color with a metallic to sub-metallic luster and a high specific gravity. It occurs in basic and ultra basic igneous rocks and in the metamorphic and sedimentary rocks that are produced when chromite-bearing rocks are altered by heat or weathering.
Chromite is important because it is the only economic ore of chromium, an essential element for a wide variety of metal, chemical and manufactured products. Many other minerals contain chromium, but none of them are found in deposits that can be economically excavate to produce chromium.
Normal analysis for Chrome ore can be as follow:
– Chemical Composition:
- Cr2O3: 28.00% – 48.00% (Bellow 28% reject)
- SiO2: 12.00% Max
- Al2O3: 14.00% Max
- Cr/Fe: 2.5% Min
- MgO: 23.00% Max
- S: 0.09% Max
- P: 0.09% Max
– Physical Composition (on Natural Basis):
- Acceptable Size: 0 -300 mm (bellow 10mm: 20% – above 10mm: 80% in AVERAGE)
– Moisture: 3.00% Max
Uses of Chromite and Chromium
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 plating on auto parts, appliances and other products. Chromium is also vital in the aerospace industry because it is used to anodize the aluminum that is used to build aircraft and related equipment. These are given the name “chrome plated.” It is also used to make super-alloys that can perform well in the hot, corrosive, and high-stress environment of jet engines.