Glossary

Chromium ore is the natural mineral source of chromium, an essential metallic element used to make stainless steel, superalloys, and industrial coatings. The main chromium ore is chromite, with the chemical formula FeCr₂O₄—an iron chromium oxide. It’s the only commercially significant ore of chromium and the raw material from which nearly all chromium-based metals, chemicals, and alloys are derived.

Composition and Structure

Chromite is a hard, dense, black-to-brownish-black mineral belonging to the spinel group. Its structure consists of:

- Iron (Fe²⁺) ions occupying one set of sites,

- Chromium (Cr³⁺) ions occupying another,

- and oxygen (O²⁻) forming the lattice.

The general chemical formula can vary slightly due to natural substitutions—magnesium, aluminum, and other elements often replace some of the iron and chromium atoms, resulting in slight compositional differences depending on the deposit.

Processing and Production

After mining, chromite ore is refined through several steps:

- Concentration: Crushing, grinding, and separating the chromite from gangue minerals.

- Smelting: In a ferrochrome furnace, chromite is combined with carbon (usually coke) and fluxes to produce ferrochrome (FeCr)—an alloy of iron and chromium.

- Refining: The ferrochrome is then used in stainless steel and other chromium-containing alloys.

Industrial Uses of Chromium Derived from Ore

- Stainless steel: Chromium gives steel its corrosion resistance and shiny finish.

- Alloy steels: Improves hardness, wear resistance, and high-temperature strength.

- Electroplating (chrome plating): For decorative and protective coatings.

- Pigments: Produces vivid green, yellow, and red colors in paints, ceramics, and glass.

- Refractory materials: Used to line furnaces because of its heat resistance.