Bauxite

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Bauxite is the aluminium ore from which most aluminium is extracted. This form of rock consists mostly of the minerals gibbsite Al(OH)3, boehmite γ-AlO(OH), and diaspore α-AlO(OH), in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2. Bauxite was named after the village Les Baux in southern France, where it was first recognised as containing aluminium and named by the French geologist Pierre Berthier in 1821.

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Bauxite formation

Lateritic bauxites (silicate bauxites) are distinguished from karst bauxite ores (carbonate bauxites). The early discovered carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of intercalated clays or by clay dissolution residues of the limestone.

The lateritic bauxites are found mostly in the countries of the tropics.They were formed by lateritization (see laterite) of various silicate rocks such as granite, gneiss, basalt, syenite, and shale. In comparison with the iron-rich laterites, the formation of bauxites demands even more intense weathering conditions in a location with very good drainage. This enables the dissolution of the kaolinite and the precipitation of the gibbsite. Zones with highest aluminium content are frequently located below a ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.

Production trends

In 2007, Australia was one of the top producers of bauxite with almost one-third of the world's production, followed by China, Brazil, Guinea, and India. Although aluminium demand is rapidly increasing, known reserves of its bauxite ore are sufficient to meet the worldwide demands for aluminium for many centuries. Increased aluminium recycling, which has the advantage of lowering the cost in electric power in producing aluminium, will considerably extend the world's bauxite reserves.

The following table is ranked by total proven bauxite reserves.

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