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bauxite
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{{about|the ore|the town in Arkansas|Bauxite, Arkansas}}File:BauxiteUSGOV.jpg|thumb|Bauxite with US penny for comparison]]File:Qemscan pisoliths.png|thumb|QEMSCAN mineral maps of bauxite ore-forming pisolithpisolithBauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite and haematite, the aluminium clay mineral kaolinite and small amounts of anatase (TiO2) and ilmenite (FeTiO3 or FeO.TiO2).Geological Survey Professional Paper page b20{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}The Clay Minerals Society Glossary for Clay Science Project {{webarchive|url=https://web.archive.org/web/20160416024036weblink |date=2016-04-16 }}In 1821 the French geologist Pierre Berthier discovered bauxite near the village of Les Baux in Provence, southern France.P. Berthier (1821) "Analyse de l'alumine hydratée des Beaux, département des Bouches-du-Rhóne" (Analysis of hydrated alumina from Les Beaux, department of the Mouths-of-the-Rhone), Annales des mines, 1st series, 6 : 531-534. Notes:
  • In 1847, in the cumulative index of volume 3 of his series, Traité de minéralogie, French mineralogist Armand Dufrénoy listed the hydrated alumina from Les Beaux as "beauxite". (See: A. Dufrénoy, Traité de minéralogie, volume 3 (Paris, France: Carilian-Goeury et Vor Dalmont, 1847), p. 799.)
  • In 1861, H. Sainte-Claire Deville credits Berthier with naming "bauxite", on p. 309, "Chapitre 1. Minerais alumineux ou bauxite" of: H. Sainte-Claire Deville (1861) "De la présence du vanadium dans un minerai alumineux du midi de la France. Études analytiques sur les matières alumineuses." (On the presence of vanadium in an alumina mineral from the Midi of France. Analytical studies of aluminous substances.), Annales de Chimie et de Physique, 3rd series, 61 : 309-342.{{Primary source inline|reason=Berthier (1821) only claims in his own research article about his find of bauxite at Les Beaux in France: "L'hydrate d'alumine n'ayant pas encore que je sache été trouvé en Europe" (Aluminium hydrate, as far as I know, has not yet been found in Europe) - independent confirmation required if first bauxite in France or first bauxite in Europe or first bauxite in world| date=September 2018}}

Formation

(File:Bauxite with unweathered rock core. C 021.jpg|thumb|left|Bauxite with core of unweathered rock)Numerous classification schemes have been proposed for bauxite but, {{As of|1982|lc=y}}, there was no consensus.BOOK, Karst Bauxites, Elsevier, Bárdossy, G., 1982, Amsterdam, 16, 978-0-444-99727-2, Vadász (1951) distinguished lateritic bauxites (silicate bauxites) from karst bauxite ores (carbonate bauxites):
  • The lateritic bauxites are found mostly in the countries of the tropics. They were formed by lateritization of various silicate rocks such as granite, gneiss, basalt, syenite, and shale. In comparison with the iron-rich laterites, the formation of bauxites depends even more on intense weathering conditions in a location with very good drainage. This enables the dissolution of the kaolinite and the precipitation of the 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.
In the case of Jamaica, recent analysis of the soils showed elevated levels of cadmium, suggesting that the bauxite originates from recent Miocene ash deposits from episodes of significant volcanism in Central America.

Production trends

{{See also|List of countries by bauxite production}}(File:2005bauxite.png|thumb|upright=1.8|Bauxite output in 2005)File:Weipa-bauxite-mine.jpg|thumb|One of the world's largest bauxite mines in Weipa, Australia]]Australia is the largest producer of bauxite, followed by China.BOOK,weblink U.S. Geological Survey, Mineral Commodity Summaries, January 2018, U.S. Geological Survey, 2018, 30–31, In 2017, China was the top producer of aluminium with almost half of the world's production, followed by Russia, Canada, and Indiaweblink Although aluminium demand is rapidly increasing, known reserves of its bauxite ore are sufficient to meet the worldwide demands for aluminium for many centuries.WEB,weblink Bauxite and Alumina, U.S. Geological Survey, 2, 9 January 2014, Increased aluminium recycling, which has the advantage of lowering the cost in electric power in producing aluminium, will considerably extend the world's bauxite reserves.{| class="wikitable sortable" style="text-align:right"Metric Tonne>Mg! Country! Mine production! Reserves
Guinea45,0007,400,000
Australia83,0006,000,000
Vietnam2,0003,700,000
Brazil36,0002,600,000
Jamaica8,1002,000,000
China68,0001,000,000
Indonesia3,6001,000,000
Guyana1,500850,000
India27,000830,000
Russia5,600500,000
Greece1,800250,000
Saudi Arabia3,900210,000
Kazakhstan5,000160,000
Malaysia1,000110,000
United StatesW{{efn|20,000
Other countries9,0303,200,000
World total (rounded)300,00030,000,000
{{notelist}}In November 2010, Nguyen Tan Dung, the prime minister of Vietnam, announced that Vietnam's bauxite reserves might total 11,000 Mt (11 trillion kg); this would be the largest in the world.WEB,weblink 2010-11-28, Mining Journal - Vietnam's bauxite reserves may total 11 billion tonnes, yes,weblink" title="web.archive.org/web/20110616203641weblink">weblink 2011-06-16,

Processing

File:CaboRojoDRBauxite.jpg|thumb|upright=1.3|Bauxite being loaded at Cabo Rojo, Dominican RepublicDominican Republic(File:Bauxite being digested by washing with hot Sodium Hydroxide.webm|thumb|Bauxite being digested by washing with a hot solution of sodium hydroxide at {{convert|175|C}} under pressure at National Aluminium Company, Nalconagar, India.)Bauxite is usually strip mined because it is almost always found near the surface of the terrain, with little or no overburden. {{As of|2010}}, approximately 70% to 80% of the world's dry bauxite production is processed first into alumina and then into aluminium by electrolysis.WEB,weblink BBC - GCSE Bitesize: Making aluminium, en-GB, 2018-04-01,weblink" title="web.archive.org/web/20180225224144weblink">weblink 2018-02-25, yes, Bauxite rocks are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical, and refractory.Usually, bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution at a temperature of {{cvt|150|to|200|°C|-1|}}. At these temperatures, the aluminium is dissolved as sodium aluminate (the Bayer process). The aluminium compounds in the bauxite may be present as gibbsite(Al(OH)3), boehmite(AlOOH) or diaspore(AlOOH); the different forms of the aluminium component will dictate the extraction conditions. The undissolved waste, bauxite tailings, after the aluminium compounds are extracted contains iron oxides, silica, calcia, titania and some un-reacted alumina. After separation of the residue by filtering, pure gibbsite is precipitated when the liquid is cooled, and then seeded with fine-grained aluminium hydroxide. The gibbsite is usually converted into aluminium oxide, Al2O3, by heating in rotary kilns or fluid flash calciners to a temperature in excess of {{cvt|1000|°C||||}}. This aluminium oxide is dissolved at a temperature of about {{cvt|960|°C||||}} in molten cryolite. Next, this molten substance can yield metallic aluminium by passing an electric current through it in the process of electrolysis, which is called the Hall–Héroult process, named after its American and French discoverers.Prior to the invention of this process, and prior to the Deville process, aluminium ore was refined by heating ore along with elemental sodium or potassium in a vacuum. The method was complicated and consumed materials that were themselves expensive at that time. This made early elemental aluminium more expensive than gold.WEB,weblink Aluminium versus aluminum, Michael Quinion, Worldwidewords.org, 2006-01-23, 2011-12-19,

Source of gallium

Bauxite is the main source of the rare metal gallium.WEB,weblink Compilation of Gallium Resource Data for Bauxite Deposits Author: USGS, 2017-12-01, During the processing of bauxite to alumina in the Bayer process, gallium accumulates in the sodium hydroxide liquor. From this it can be extracted by a variety of methods. The most recent is the use of ion-exchange resinJOURNAL, Frenzel, Max, Ketris, Marina P., Seifert, Thomas, Gutzmer, Jens, March 2016, On the current and future availability of gallium,weblink Resources Policy, 47, 38–50, 10.1016/j.resourpol.2015.11.005, . Achievable extraction efficiencies critically depend on the original concentration in the feed bauxite. At a typical feed concentration of 50 ppm, about 15 percent of the contained gallium is extractable. The remainder reports to the red mud and aluminium hydroxide streams.JOURNAL, Moskalyk, R. R., 2003, Gallium: the backbone of the electronics industry, Minerals Engineering, 16, 10, 921–929, 10.1016/j.mineng.2003.08.003,

See also

{{Wikipedia books|Aluminium}}

References

{{Reflist}}

Further reading

  • Bárdossy, G. (1982): Karst Bauxites: Bauxite deposits on carbonate rocks. Elsevier Sci. Publ. 441 p.
  • Bárdossy, G. and Aleva, G.J.J. (1990): Lateritic Bauxites. Developments in Economic Geology 27, Elsevier Sci. Publ. 624 p. {{ISBN|0-444-98811-4}}
  • Grant, C.; Lalor, G. and Vutchkov, M. (2005) Comparison of bauxites from Jamaica, the Dominican Republic and Suriname. Journal of Radioanalytical and Nuclear Chemistry p. 385–388 Vol.266, No.3
  • Hanilçi, N. (2013). Geological and geochemical evolution of the BolkardaÄŸi bauxite deposits, Karaman, Turkey: Transformation from shale to bauxite. Journal of Geochemical Exploration

External links

{{commons category|Bauxite}} {{ores}}{{Industry country lists|state=collapsed}}{{Authority control}}

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