Difference between revisions of "Bauxite" - New World Encyclopedia
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− | [[Image:BauxiteUSGOV.jpg|thumb|Bauxite with penny]] | + | {{Claimed}}{{Started}} |
− | [[Image:Bauxite with unweathered rock core. C 021.jpg|thumb|Bauxite with core of unweathered rock]] | + | [[Image:BauxiteUSGOV.jpg|thumb|250px|Bauxite with penny]] |
− | '''Bauxite''' is an [[ | + | [[Image:Bauxite with unweathered rock core. C 021.jpg|thumb|250px|Bauxite with core of unweathered rock]] |
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+ | '''Bauxite''' is an [[aluminum]] [[ore]]. It consists largely of the aluminum minerals [[gibbsite]] Al(OH)<sub>3</sub>, [[boehmite]] and [[diaspore]] AlOOH, together with the iron oxides [[goethite]] and [[hematite]], the clay mineral [[kaolinite]] and small amounts of [[anatase]] TiO<sub>2</sub>. It was named after the village Les Baux-de-Provence in southern France, where it was first discovered in 1821 by geologist Henri Rouvère. | ||
==Formation== | ==Formation== | ||
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==See also== | ==See also== | ||
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+ | * [[Aluminum]] | ||
+ | * [[Mineral]] | ||
+ | * [[Ore]] | ||
+ | * [[Rock (geology)]] | ||
==External links== | ==External links== | ||
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* [http://minerals.usgs.gov/minerals/pubs/commodity/bauxite/ USGS Minerals Information: Bauxite] | * [http://minerals.usgs.gov/minerals/pubs/commodity/bauxite/ USGS Minerals Information: Bauxite] | ||
*[http://www.mii.org/Minerals/photoal.html Mineral Information Institute] | *[http://www.mii.org/Minerals/photoal.html Mineral Information Institute] | ||
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− | [[Category: | + | [[Category:Earth sciences]] |
+ | [[Category:Geology]] | ||
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Revision as of 07:23, 21 February 2007
Bauxite is an aluminum ore. It consists largely of the aluminum minerals gibbsite Al(OH)3, boehmite and diaspore AlOOH, 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 Henri Rouvère.
Formation
In geosciences 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 either 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 granites, gneisses, basalts, syenite, clays and shales. Compared with Fe-rich laterites the formation of bauxites demands even stronger weathering conditions with a very good drainage. This enables dissolution of kaolinite and precipitation of gibbsite. Zones with highest Al contents are frequently located below a feruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.
World bauxite mine production, reserves, and reserve base
Country | Mine production | Reserves | Reserve base | |
---|---|---|---|---|
2000 | 2001 | |||
Australia | 200–800 | 53,500 | 3,800,000 | 7,400,000 |
Brazil | 14,000 | 14,000 | 3,900,000 | 4,900,000 |
People's Republic of 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 |
World total (rounded) | 135,000 | 137,000 | 24,000,000 | 34,000,000 |
Processing
Approx. 95% of the world 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 very energy-consumptive electrolytic process (Hall-Héroult process).
ReferencesISBN links support NWE through referral fees
- Bardossy, G. (1882): 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
See also
External links
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