Bauxite is the most important
aluminium ore. It consists largely of the minerals gibbsiteAl(OH)3, boehmiteγ-AlO(OH), and diasporeα-AlO(OH), together with the iron oxides goethiteand hematite, the clay mineral kaoliniteand small amounts of anataseTiO2. It was named after the village Les Bauxin southern France, where it was first discovered in 1821 by the geologist Pierre Berthier.
Lateritic bauxites (silicate bauxites) are distinguished from
karstbauxites (carbonate bauxites). The early discovered carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks ( limestoneand dolomite), where they were formed by lateritic weatheringand residual accumulation of intercalated clays or of clayey dissolution residues of the limestone.
The lateritic bauxites occur in many countries of the tropical belt. They were formed by lateritization (see
laterite) of various silicate rocks such as granite, gneiss, basalt, syeniteand shale. Compared with iron-rich laterites, the formation of bauxites demands even more intense weathering conditions with a very good drainage. This enables dissolution of kaolinite and precipitation of gibbsite. Zones with highest aluminium content are frequently located below a ferruginoussurface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.
In 2007, Australia was the top producer of bauxite with almost one-third world share, followed by China, Brazil, Guinea, and Jamaica. Although aluminium demand is rapidly increasing, known reserves are sufficient to meet the needs for a considerable length of time. Increased aluminium recycling, which has the advantage of lowering the energy costs of production, will help extend bauxite reserves. Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2008
Bauxite is strip mined (
surface mining) because it is found at the surface, with little or no overburden. Approximately 95% of the world's bauxite production is processed into aluminium. Bauxites are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical and refractory.
Bauxites are heated in pressure vessels with
sodium hydroxidesolution at 150-200 °C through which aluminiumis dissolved as aluminate ( Bayer process). After separation of ferruginous residue (red mud) by filtering, pure gibbsite is precipitated when the liquor is cooled and seeded with fine grained aluminium hydroxide. Gibbsite is converted into aluminium oxideby heating. This is molten at approx. 1000 °C by addition of cryoliteas a flux and reduced to metallic aluminium by a highly energy-consumptive electrolyticprocess (the Hall-Héroult process).
*Bardossy, G. (1982): Karst Bauxites. Bauxite deposits on carbonate rocks. Elsevier Sci. Publ. 441 p.
*Bardossy, G. and Aleva, G.J.J. (1990): Lateritic Bauxites. Developments in Economic Geology 27, Elsevier Sci. Publ. 624 p. ISBN 0-444-98811-4
* [http://minerals.usgs.gov/minerals/pubs/commodity/bauxite/ USGS Minerals Information: Bauxite]
* [http://www.mii.org/Minerals/photoal.html Mineral Information Institute]
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Bauxite — ou minerai d aluminium Bauxite (Hérault) avec des pisolites … Wikipédia en Français
bauxite — [ boksit ] n. f. • 1847; des Baux de Provence ♦ Roche siliceuse alumineuse formée surtout d alumine, plus ou moins riche en oxydes de fer (bauxite rouge), en titane et en vanadium. La bauxite, principal minerai d aluminium. ● bauxite nom féminin… … Encyclopédie Universelle
Bauxite — Bauxite, AR U.S. town in Arkansas Population (2000): 432 Housing Units (2000): 171 Land area (2000): 2.392685 sq. miles (6.197025 sq. km) Water area (2000): 0.056432 sq. miles (0.146158 sq. km) Total area (2000): 2.449117 sq. miles (6.343183 sq.… … StarDict's U.S. Gazetteer Places
Bauxite, AR — U.S. town in Arkansas Population (2000): 432 Housing Units (2000): 171 Land area (2000): 2.392685 sq. miles (6.197025 sq. km) Water area (2000): 0.056432 sq. miles (0.146158 sq. km) Total area (2000): 2.449117 sq. miles (6.343183 sq. km) FIPS… … StarDict's U.S. Gazetteer Places
bauxite — 1861, clayey mineral containing aluminum, from Fr. bauxite (1821), from Les Baux, near Soles, where it was first found. The place name is from Prov. Li Baus, lit. the precipices … Etymology dictionary
Bauxite — Baux ite, Beauxite Beaux ite,n. [F., fr. Baux or Beaux, near Arles.] (Min.) A ferruginous hydrate of alumina. It is the most commonly used ore for the preparation of aluminum and alumina. It is also used for the lining of furnaces which are… … The Collaborative International Dictionary of English
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bauxite — [bôks′īt΄, bō′zīt΄] n. [Fr, after (Les) Baux, town near Arles, France] a soft, claylike sedimentary rock, mainly hydrous aluminum hydroxide, that is the chief ore of aluminum … English World dictionary