AskDefine | Define bauxite

Dictionary Definition

bauxite n : a clay-like mineral; the chief ore of aluminum; composed of aluminum oxides and aluminum hydroxides; used as an abrasive and catalyst

User Contributed Dictionary

English

Etymology

from Les Baux in France

Noun

bauxite
  1. the principal ore of aluminium; a clay-like mineral, being a mixture of hydrated oxides and hydroxides

Translations

ore
  • Croatian: boksit

Extensive Definition

Bauxite is the most important aluminium ore. It consists largely of the minerals gibbsite Al(OH)3, boehmite γ-AlO(OH), and diaspore α-AlO(OH), together with the iron oxides goethite and hematite, the clay mineral kaolinite and small amounts of anatase TiO2. It was named after the village Les Baux-de-Provence in southern France, where it was first discovered in 1821 by geologist Pierre Berthier.

Bauxite formation

Lateritic bauxites (silicate bauxites) are distinguished from karst bauxites (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 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, syenite and 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 ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.

Production trends

In 2007, Australia was the top producer of bauxite with almost one-third world share, followed by China, Brazil, Guinea and Jamaica. Although aluminum demand is rapidly increasing, known reserves are sufficient to meet the needs for a considerable time. Increased aluminum 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

Processing

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 hydroxide solution at 150-200 °C through which aluminium is 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 oxide by heating. This is molten at approx. 1000 °C by addition of cryolite as a flux and reduced to metallic aluminium by a highly energy-consumptive electrolytic process (the Hall-Héroult process).

References

  • 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
bauxite in Arabic: بوكسيت
bauxite in Bulgarian: Боксит
bauxite in Bosnian: Boksit
bauxite in Catalan: Bauxita
bauxite in Czech: Bauxit
bauxite in Danish: Bauxit
bauxite in German: Bauxit
bauxite in Modern Greek (1453-): Βωξίτης
bauxite in Estonian: Boksiit
bauxite in Spanish: Bauxita
bauxite in Esperanto: Baŭksito
bauxite in French: Bauxite
bauxite in Galician: Bauxita
bauxite in Korean: 보크사이트
bauxite in Croatian: Boksit
bauxite in Italian: Bauxite
bauxite in Hebrew: בוקסיט
bauxite in Swahili (macrolanguage): Boksiti
bauxite in Lithuanian: Boksitas
bauxite in Hungarian: Bauxit
bauxite in Malayalam: ബോക്സൈറ്റ്
bauxite in Dutch: Bauxiet
bauxite in Japanese: ボーキサイト
bauxite in Norwegian: Bauksitt
bauxite in Norwegian Nynorsk: Bauksitt
bauxite in Polish: Boksyt
bauxite in Portuguese: Bauxita
bauxite in Romanian: Bauxită
bauxite in Russian: Боксит
bauxite in Simple English: Bauxite
bauxite in Slovak: Bauxit
bauxite in Serbian: Боксит
bauxite in Finnish: Bauksiitti
bauxite in Swedish: Bauxit
bauxite in Vietnamese: Bauxit
bauxite in Turkish: Boksit
bauxite in Ukrainian: Боксити
bauxite in Chinese: 铝土矿
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