Difference between revisions of "Bauxite" - New World Encyclopedia

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[[Image:BauxiteUSGOV.jpg|thumb|250px|A sample of bauxite, placed next to a penny.]]
 
[[Image:BauxiteUSGOV.jpg|thumb|250px|A sample of bauxite, placed next to a penny.]]
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'''Bauxite''' is an important [[ore]] of [[aluminum]], composed mainly of [[aluminum oxide]] and [[hydroxide]] minerals. It was named after the village Les Baux-de-Provence in southern [[France]], where it was first discovered in 1821 by [[geology|geologist]] Henri Rouvère. Bauxites have a range of commercial applications, such as for the production of aluminum [[metal]] and aluminum-based [[chemical]]s, [[abrasive]]s, [[cement]]s, and refractory materials.
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[[Image:Bauxite with unweathered rock core. C 021.jpg|thumb|250px|Bauxite showing a core of unweathered rock.]]
 
[[Image:Bauxite with unweathered rock core. C 021.jpg|thumb|250px|Bauxite showing a core of unweathered rock.]]
 
'''Bauxite''' is an important [[ore]] of [[aluminum]]. It was named after the village Les Baux-de-Provence in southern France, where it was first discovered in 1821 by geologist Henri Rouvère.
 
  
 
== Composition ==
 
== Composition ==
  
Bauxite is composed of [[aluminum oxide]] and [[hydroxide]] minerals such as gibbsite (Al(OH)<sub>3</sub>), [[boehmite]] (AlO(OH)), and [[diaspore]] (AlO(OH)), as well as [[clay]]s (such as [[kaolinite]]), [[silt]], and [[iron oxide]]s and hydroxides. It may also contain small amounts of [[anatase]] (TiO<sub>2</sub>).
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Bauxite consists predominantly of minerals such as gibbsite (Al(OH)<sub>3</sub>), [[boehmite]] (AlO(OH)), and [[diaspore]] (AlO(OH)), as well as lesser amounts of [[clay]]s (such as [[kaolinite]]), [[silt]], and [[iron oxide]]s and hydroxides. It may also contain small amounts of [[anatase]] (TiO<sub>2</sub>).
 
 
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Bauxite is a [[laterite]], a rock formed from intense weathering environments such as found in richly forested, humid, tropical climates.
 
 
 
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"Bauxite is a naturally occurring, heterogeneous material composed primarily of one or more aluminum hydroxide minerals, plus various mixtures of silica, iron oxide, titania, aluminosilicate, and other impurities in minor or trace amounts.  The principal aluminum 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 used as feed for the manufacture of alumina via a wet chemical caustic leach method commonly known as the Bayer process.  Subsequently, the majority of the resulting alumina produced from this refining process is in turn employed as the feedstock for the production of aluminum metal by the electrolytic reduction of alumina in a molten bath of natural or synthetic cryolite (Na3AlF6), the Hall-Héroult process."
 
88888888888
 
  
 
==Formation==
 
==Formation==
  
In the 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.
+
Bauxite is a [[laterite]],<ref>A laterite is a surface formation in hot, wet tropical areas. The rock is enriched in [[iron]] and [[aluminum]] and develops by intensive, long-lasting [[weathering]] of the underlying [[parent rock]].</ref> formed by the intense weathering of surface rocks. In the geosciences, lateritic bauxites (silicate bauxites) are distinguished from [[karst]] bauxites (carbonate bauxites). In [[Europe]] and [[Jamaica]], carbonate bauxites have been found above carbonate rocks ([[limestone]] and [[dolomite]]), where they were formed by the 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.
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The lateritic (silicate) bauxites occur in many countries of the tropical belt. They were formed by lateritization of various aluminum silicate rocks, such as [[granite]]s, [[gneiss]]es, [[basalt]]s, [[syenite]], [[clay]]s, and [[shale]]s. Compared with iron-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 aluminum content are frequently located below an iron-rich surface layer. The aluminum hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.
  
== Processing and applications ==
+
== Processing ==
  
Approximately 95 percent of the world's bauxite production is processed into [[aluminum]]. Bauxites are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical, and refractory.
+
The bulk of the world's bauxite production is processed into alumina (aluminum oxide) and then into aluminum. In the [[Bayer process]], bauxites are heated in pressure vessels with sodium hydroxide solution at 150-200 °C. As a result, the aluminum in the ore is dissolved as aluminate, and the iron-rich residue (red mud) is separated by filtering. The liquor is then cooled, and pure gibbsite is precipitated by seeding with fine-grained aluminum hydroxide. Gibbsite is converted into aluminum oxide by heating. This product is molten at approximately 1000 °C by adding [[cryolite]] (Na<sub>3</sub>AlF<sub>6</sub>) as a flux, and it is reduced to metallic aluminum by an [[electrolysis|electrolytic]] process called the [[Hall-Héroult process]].
 
 
In the [[Bayer process]], bauxites are heated in pressure vessels with sodium hydroxide solution at 150-200 °C. As a result, the aluminum in the ore is dissolved as aluminate. The ferruginous (iron-rich) residue (red mud) is separated by filtering, and pure gibbsite is precipitated when the liquor is cooled and seeded with fine-grained aluminum hydroxide. Gibbsite is converted into aluminum oxide by heating. This product is molten at approximately 1000 °C by adding[[cryolite]] as a flux, and it is reduced to metallic aluminum by a very energy-consumptive [[electrolytic]] process called the [[Hall-Héroult process]].
 
  
 
== World bauxite mine production, reserves, and reserve base ==
 
== World bauxite mine production, reserves, and reserve base ==
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! 2001
 
! 2001
 
|-
 
|-
| [[Australia]] ||           200–800 || 53,500 || 3,800,000 ||   7,400,000
+
| [[Australia]] ||     200–800 || 53,500 || 3,800,000 || 7,400,000
 
|-
 
|-
| [[Brazil]]   ||             14,000 || 14,000 || 3,900,000 ||   4,900,000
+
| [[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
+
| [[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
+
| [[Guinea]] ||       15,000 || 15,000 || 7,400,000 || 8,600,000
 
|-
 
|-
| [[Guyana]]   ||               2,400 || 2,000 ||   700,000 ||     900,000
+
| [[Guyana]] ||       2,400 || 2,000 || 700,000 ||   900,000
 
|-
 
|-
| [[India]]   ||               7,370 || 8,000 ||   770,000 ||   1,400,000
+
| [[India]] ||       7,370 || 8,000 || 770,000 || 1,400,000
 
|-
 
|-
| [[Jamaica]] ||             11,100 || 13,000 || 2,000,000 ||   2,500,000
+
| [[Jamaica]] ||       11,100 || 13,000 || 2,000,000 || 2,500,000
 
|-
 
|-
| [[Russia]]   ||               4,200 || 4,000 ||   200,000 ||     250,000
+
| [[Russia]] ||       4,200 || 4,000 || 200,000 ||   250,000
 
|-
 
|-
| [[Suriname]] ||               3,610 || 4,000 ||   580,000 ||     600,000
+
| [[Suriname]] ||       3,610 || 4,000 || 580,000 ||   600,000
 
|-
 
|-
| [[United States]]   ||         NA   ||   NA   ||   20,000 ||     40,000
+
| [[United States]] ||     NA || NA || 20,000 ||   40,000
 
|-
 
|-
| [[Venezuela]] ||             4,200 || 4,400 ||   320,000 ||     350,000
+
| [[Venezuela]] ||       4,200 || 4,400 || 320,000 ||   350,000
 
|-
 
|-
| Other countries ||       10,800 || 10,200 || 4,100,000 ||   4,700,000
+
| 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
+
| World total (rounded)|| 135,000 || 137,000 || 24,000,000 || 34,000,000
 
|}
 
|}
  
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* [[Ore]]
 
* [[Ore]]
 
* [[Rock (geology)]]
 
* [[Rock (geology)]]
 +
 +
== Notes ==
 +
<references/>
  
 
== References ==
 
== References ==
  
* Bardossy, Gyorgy, 1982. ''Karst Bauxites: Bauxite Deposits on Carbonate Rocks''. Elsevier Science. ISBN 044499727X and ISBN 978-0444997272.
+
* Bardossy, Gyorgy. ''Karst Bauxites: Bauxite Deposits on Carbonate Rocks''. Elsevier Science, 1982. ISBN 044499727X
 
+
* Bardossy, Gyorgy, and G.J.J. Aleva. ''Lateritic Bauxites. Developments in Economic Geology'' 27, Elsevier, 1990. ISBN 0444988114
* Bardossy, Gyorgy, and G.J.J. Aleva, 1990. ''Lateritic Bauxites. Developments in Economic Geology'' 27, Elsevier. ISBN 0444988114 and ISBN 978-0444988119.
+
* Kogel, Jessica Elzea, Nikhil C. Trivedi, James M. Barker, and Stanley T. Krukowski (editors). ''Industrial Minerals & Rocks: Commodities, Markets, and Uses'', Seventh Edition. Littleton, CO: Society for Mining, Metallurgy, and Exploration, 2006. ISBN 0873352335
 
+
* Misra, Kula C. ''Understanding Mineral Deposits''. Dordrecht, the Netherlands: Kluwer Academic Publishers, 2000. ISBN 0045530092
* Kogel, Jessica Elzea, Nikhil C. Trivedi, James M. Barker, and Stanley T. Krukowski (editors), 2006. ''Industrial Minerals & Rocks: Commodities, Markets, and Uses'' (Seventh Edition). Littleton, CO: Society for Mining, Metallurgy, and Exploration. ISBN 0873352335 and ISBN 978-0873352338.
+
* Moon, Charles J., Michael E.G. Whateley, and Anthony M. Evans (editors). ''Introduction to Mineral Exploration'', Second Edition. Malden, MA: Blackwell Publishing, 2006. ISBN 1405113170
 
+
* Nesse, William D. ''Introduction to Mineralogy''. Oxford, UK; New York, NY: Oxford University Press, 2000. ISBN 0195106911
* Misra, Kula C., 2000. ''Understanding Mineral Deposits''. Dordrecht, the Netherlands: Kluwer Academic Publishers. ISBN 0045530092 and ISBN 978-0045530090.
 
 
 
* Moon, Charles J., Michael E.G. Whateley, and Anthony M. Evans (editors), 2006. ''Introduction to Mineral Exploration'' (Second Edition). Malden, MA: Blackwell Publishing. ISBN 1405113170 and ISBN 978-1405113175.
 
 
 
* Nesse, William D., 2000. ''Introduction to Mineralogy''. Oxford, UK; New York, NY: Oxford University Press. ISBN 0195106911 and ISBN 978-0195106916.
 
  
 
==External links==
 
==External links==
 
+
All links retrieved January 16, 2022.
* [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]
+
  
 
[[Category:Physical sciences]]
 
[[Category:Physical sciences]]

Revision as of 22:17, 16 January 2022


A sample of bauxite, placed next to a penny.

Bauxite is an important ore of aluminum, composed mainly of aluminum oxide and hydroxide minerals. It was named after the village Les Baux-de-Provence in southern France, where it was first discovered in 1821 by geologist Henri Rouvère. Bauxites have a range of commercial applications, such as for the production of aluminum metal and aluminum-based chemicals, abrasives, cements, and refractory materials.

Bauxite showing a core of unweathered rock.

Composition

Bauxite consists predominantly of minerals such as gibbsite (Al(OH)3), boehmite (AlO(OH)), and diaspore (AlO(OH)), as well as lesser amounts of clays (such as kaolinite), silt, and iron oxides and hydroxides. It may also contain small amounts of anatase (TiO2).

Formation

Bauxite is a laterite,[1] formed by the intense weathering of surface rocks. In the geosciences, lateritic bauxites (silicate bauxites) are distinguished from karst bauxites (carbonate bauxites). In Europe and Jamaica, carbonate bauxites have been found above carbonate rocks (limestone and dolomite), where they were formed by the weathering either of intercalated clays or of clayey dissolution residues of the limestone.

The lateritic (silicate) bauxites occur in many countries of the tropical belt. They were formed by lateritization of various aluminum silicate rocks, such as granites, gneisses, basalts, syenite, clays, and shales. Compared with iron-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 aluminum content are frequently located below an iron-rich surface layer. The aluminum hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.

Processing

The bulk of the world's bauxite production is processed into alumina (aluminum oxide) and then into aluminum. In the Bayer process, bauxites are heated in pressure vessels with sodium hydroxide solution at 150-200 °C. As a result, the aluminum in the ore is dissolved as aluminate, and the iron-rich residue (red mud) is separated by filtering. The liquor is then cooled, and pure gibbsite is precipitated by seeding with fine-grained aluminum hydroxide. Gibbsite is converted into aluminum oxide by heating. This product is molten at approximately 1000 °C by adding cryolite (Na3AlF6) as a flux, and it is reduced to metallic aluminum by an electrolytic process called the Hall-Héroult process.

World bauxite mine production, reserves, and reserve base

(x1000 tonne, Numbers for 2001 estimated)
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

See also

Notes

  1. A laterite is a surface formation in hot, wet tropical areas. The rock is enriched in iron and aluminum and develops by intensive, long-lasting weathering of the underlying parent rock.

References
ISBN links support NWE through referral fees

  • Bardossy, Gyorgy. Karst Bauxites: Bauxite Deposits on Carbonate Rocks. Elsevier Science, 1982. ISBN 044499727X
  • Bardossy, Gyorgy, and G.J.J. Aleva. Lateritic Bauxites. Developments in Economic Geology 27, Elsevier, 1990. ISBN 0444988114
  • Kogel, Jessica Elzea, Nikhil C. Trivedi, James M. Barker, and Stanley T. Krukowski (editors). Industrial Minerals & Rocks: Commodities, Markets, and Uses, Seventh Edition. Littleton, CO: Society for Mining, Metallurgy, and Exploration, 2006. ISBN 0873352335
  • Misra, Kula C. Understanding Mineral Deposits. Dordrecht, the Netherlands: Kluwer Academic Publishers, 2000. ISBN 0045530092
  • Moon, Charles J., Michael E.G. Whateley, and Anthony M. Evans (editors). Introduction to Mineral Exploration, Second Edition. Malden, MA: Blackwell Publishing, 2006. ISBN 1405113170
  • Nesse, William D. Introduction to Mineralogy. Oxford, UK; New York, NY: Oxford University Press, 2000. ISBN 0195106911

External links

All links retrieved January 16, 2022.

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