Bauxite

From Open Encyclopedia

Image:BauxiteUSGOV.jpg Image:Mineraly.sk - bauxit.jpg Bauxite is a naturally occurring, heterogeneous material composed primarily of one or more aluminium hydroxide minerals, plus various mixtures of silica, iron oxide, titania, aluminium silicates, and other impurities in minor or trace amounts. Bauxite is a sedimentary rock produced by in situ chemical weathering typically under tropical to subtropical climate conditions.

The principal aluminium hydroxide minerals found in varying proportions with bauxites are gibbsite and the polymorphs boehmite and diaspore. Bauxites are typically classified according to their intended commercial application: abrasive, cement, chemical, metallurgical, refractory, etc.

The bulk of world bauxite production (approximately 85%) is processed into aluminium oxide (Al₂O₃, also known as alumina) via a wet chemical, caustic leach method (the Bayer process). The resulting Al₂O₃ is then reduced to aluminium metal (Al) using an electrolytic process, the Hall-Heroult process.

Bauxite is the raw material most widely used in the production of aluminium on a commercial scale. Other raw materials, such as anorthosite, alunite, coal wastes, and oil shales, offer additional potential Al₂O₃ sources. Although it would require new facilities and technology, Al₂O₃ from these nonbauxitic materials could satisfy the demand for primary metal, refractories, aluminium chemicals, and abrasives. Synthetic mullite, produced from kyanite and sillimanite, substitutes for bauxite-based refractories. Although more costly, silicon carbide and alumina-zirconia substitute for bauxite-based abrasives.

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History

Bauxite was named after the village Les Baux de Provence in southern France, where it was first discovered in 1821 by the geologist Pierre Berthier.

Due to the exhaustion of its bauxite mines, France has almost completely ceased the exploitation of bauxite since 1991. French mines were located in the Var, Bouches-du-Rhône and Herault départements.

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World Bauxite Mine Production, Reserves, and Reserve Base

(x1000 tonne)
                       Mine production    Reserves    Reserve base
                        2000     2001
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Australia              53,800   53,500   3,800,000     7,400,000
Brazil                 14,000   14,000   3,900,000     4,900,000
China                   9,000    9,200     720,000     2,000,000
Guinea                 15,000   15,000   7,400,000     8,600,000
Guyana                  2,400    2,000     700,000       900,000
India                   7,370    8,000     770,000     1,400,000
Jamaica                11,100   13,000   2,000,000     2,500,000
Russia                  4,200    4,000     200,000       250,000
Suriname                3,610    4,000     580,000       600,000
United States           NA       NA         20,000        40,000
Venezuela               4,200    4,400     320,000       350,000
Other countries        10,800   10,200   4,100,000     4,700,000
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World total (rounded) 135,000  137,000  24,000,000    34,000,000