Bauxite is the primary ore of aluminum. Almost all of the aluminum that has ever been produced has been extracted from bauxite. The United States has a few small bauxite deposits but at least 99% of the bauxite used in the United States is imported. The United States is also a major importer of aluminum metal.

Many people are surprised to learn that bauxite is not a mineral. It is a rock composed mainly of aluminum-bearing minerals. It forms when laterite soils are severely leached of silica and other soluble materials in a wet tropical or subtropical climate.

Chemical Composition of Bauxite

Bauxite does not have a specific composition. It is a mixture of hydrous aluminium oxides, aluminium hydroxides, clay minerals, and insoluble materials such as quartz, hematite, magnetite, siderite, and goethite. The aluminium minerals in bauxite can include gibbsite Al(OH)3, boehmite AlO(OH), and diaspore, AlO(OH).

Physical Properties of Bauxite

Bauxite appears dull in lustre and is reddish brown, white or tan in colour. The Mohs hardness of bauxite is 1 to 3, which means it is a very soft material. The specific gravity is around 2 to 2.5. Bauxite is always processed into other materials with physical properties that are extremely different from bauxite.

Uses of Bauxite:

In Metallurgy

Bauxite is the best and only material used for the production of aluminium. Aluminium production is the main use of bauxite. Once aluminium is extracted, it finds many applications in electronics, constructions, vehicles and in utensils.

The conventional steps of production of aluminium are Bayer’s process, where bauxite is converted to alumina and through the hall heroult process, aluminium produces. In the above process, 4 to 5 tonnes of dried bauxite gives 2 tonnes of alumina, and it again gives almost one ton of aluminium.

In Chemical Industry

Production of aluminium chemicals like aluminium sulphate, aluminium chloride, aluminium fluoride, sodium aluminate etc is an important use of bauxite. Bauxite is directly used to produce aluminium sulphate, which is a flocculating agent in water and effluent. Anhydrous AlCl3.6H2O is used as a catalyst in organic reactions and has metallurgical and metal finishing applications. Aluminium fluorides are used as a flux in remelting aluminium and aluminium alloys. Sodium aluminate is used for industrial water treatment.

In Refractory Industry

Bauxite is used as raw material in making refractory products since it has a melting point from 1740 to 18200C. The principal use for the refractory grade bauxite is in the production of alumina refractories containing 75 to 90% of alumina; these are used in the manufacture of bricks to lane the roof of blast furnaces and electrical and steel-making furnaces. In the copper industry, high alumina refractories are used in reverberatory furnaces. Also, the glass and cement industry uses high alumina refractories.

In Abrasive Industry

Bauxite is used in abrasive industries. The abrasive grain is produced either by the fusion of chemically purified alumina or from calcined bauxite. The product from the fused calcined bauxite is called brown fused alumina. The brown fused alumina accounts for 80 to 90% of fused alumina in the abrasive industry. It has application in bonded and coated abrasives such as grinding wheels, belt sheets and mops. The fused alumina is used to grind high-strength materials like bronze and steel.

In Cement Industry

The high alumina cement is obtained by mixing selected qualities of bauxite with limestone. These cements are known for their quality and rapid setting time. The high alumina cement sets within 3 to 4 hours and becomes strong after 24 hours. It is resistant to corrosion and resistant to sulphate and dilutes acids present in the soil, so high alumina cement is used to make tunnels, concrete piles etc.

In Absorbant Industry

Activated bauxite is used as a drying agent for gases and organic liquids hence it is suitable to use in the petroleum industry. It is used as an absorbent for a number of compounds based on sulphur and fluorine. It also has applications in the areas of catalyst and filtration.

In Steel Industry

In the steel, industry, bauxite is used to control desulphurising power and fluidity of the slag and provide material for blast furnaces of the cement during iron making. It is also used in oxygen furnaces as an additive to control the viscosity of the slag. Here bauxite is used as a source of alumina to control viscosity.

In Building Stone and Road Aggregates

Laterite bauxite is a handy substitute for building materials if no other materials are available. Calcined bauxite is used as anti-skid road aggregate, which can be used in selected locations to prevent road accidents. Using of calcined bauxite in roads hence considered as an important uses of bauxite