Ajay Kumar at 17:10, 24 August 2023

2023-08-24T17:10:45Z

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{{short description|Sedimentary rock rich in aluminium}}
{{about|the ore|the town in Arkansas|Bauxite, Arkansas}}
[[File:Bauxite hérault.JPG|thumb|Reddish-brown bauxite]]
[[File:BauxiteUSGOV.jpg|thumb|Bauxite with [[Penny (United States coin)|US penny]] for comparison]]
[[File:Qemscan pisoliths.png|thumb|[[QEMSCAN]] mineral maps of bauxite ore-forming [[pisolith]]s]]

'''Bauxite''' is a [[sedimentary rock]] with a relatively high [[aluminium]] content. It is the world's main source of [[aluminium]] and [[gallium]]. Bauxite consists mostly of the aluminium [[mineral]]s [[gibbsite]] (Al(OH)3), [[boehmite]] (γ-AlO(OH)) and [[diaspore]] (α-AlO(OH)), [[Mixture|mixed]] with the two [[iron oxide]]s [[goethite]] (FeO(OH)) and [[haematite]] (Fe2O3), the aluminium [[Clay minerals|clay mineral]] [[kaolinite]] (Al2Si2O5(OH)4) and small amounts of [[anatase]] (TiO2) and [[ilmenite]] (FeTiO3 or FeO.TiO2).<ref>{{cite web | url=http://www.clays.org/GLOSSARY/Clay_Glossary.htm | title=The Clay Minerals Society Glossary for Clay Science Project | url-status=dead | archive-url=https://web.archive.org/web/20160416024036/http://www.clays.org/GLOSSARY/Clay_Glossary.htm | archive-date=2016-04-16}}</ref>
Bauxite appears dull in [[Lustre (mineralogy)|luster]] and is reddish-brown, white, or tan.<ref>{{cite web | title=Aluminum | publisher=Minerals Education Coalition | url=https://mineralseducationcoalition.org/minerals-database/aluminum/#:~:text=Aluminum%20is%20the%20most%20abundant,gibbsite%2C%20boehmite%2C%20and%20diaspore.&text=Because%20it%20is%20a%20mixture,a%20rock%2C%20not%20a%20mineral}}</ref>

In 1821, the [[French people|French]] [[geologist]] [[Pierre Berthier]] discovered bauxite near the village of [[Les Baux-de-Provence|Les Baux]] in [[Provence]], southern [[France]].<ref>P. Berthier (1821) [https://books.google.com/books?id=53wkLqfF6tQC&pg=PA531 "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 [[Ours-Pierre-Armand Petit-Dufrénoy|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), [https://books.google.com/books?id=XxwOAAAAQAAJ&pg=PA799 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) [http://babel.hathitrust.org/cgi/pt?id=hvd.hx3dz6;view=1up;seq=321 "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.</ref><ref name="Burgess_2015">{{Cite web |last=Burgess |first=N. |date=October 26, 2015 |title=March 23, 1821: Bauxite Discovered |url=https://www.earthmagazine.org/article/march-23-1821-bauxite-discovered/ |access-date=2021-07-31 |publisher=Earth}}</ref>

== Formation ==
[[File:Bauxite with unweathered rock core. C 021.jpg|thumb|Bauxite with core of unweathered rock]]
Numerous classification schemes have been proposed for bauxite but, {{As of|1982|lc=y}}, there was no consensus.<ref name="BatdossyKarst1982">{{cite book | title=Karst Bauxites | publisher=Elsevier | author=Bárdossy, G. | year=1982 | location=Amsterdam | pages=16 | isbn=978-0-444-99727-2}}</ref>

Vadász (1951) distinguished [[Laterite|lateritic]] bauxites (silicate bauxites) from [[karst]] bauxite [[ore]]s (carbonate bauxites):<ref name="BatdossyKarst1982"/>

* The carbonate bauxites occur predominantly in [[Europe]], [[Guyana]], [[Suriname]], and [[Jamaica]] above [[carbonate rock]]s ([[limestone]] and [[Dolomite (mineral)|dolomite]]), where they were formed by lateritic [[weathering]] and residual accumulation of intercalated [[clay]] layers – dispersed clays which were concentrated as the enclosing limestones gradually dissolved during [[chemical weathering]].
* The lateritic bauxites are found mostly in the countries of the [[tropics]]. They were formed by [[lateritization]] of various [[Silicate#Silicate rock|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 [[Iron oxide|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 [[Miocene]] [[volcanic ash]] deposits from episodes of significant volcanism in Central America.{{cn|date=July 2022}}

==Production and reserves==
{{Main|List of countries by bauxite production}}

[[File:2005bauxite.png|thumb|upright=1.8|World bauxite production in 2005]]

[[File:Weipa-bauxite-mine.jpg|thumb|upright=1.3|One of the world's largest bauxite mines in [[Weipa]], in northern [[Queensland]], Australia]]

Australia is the largest producer of bauxite, followed by [[Guinea]] and [[China]].<ref name="usgs_2020">{{Cite web|date=January 2020|title=Bauxite and Alumina 2020 Annual Publication|url=https://pubs.usgs.gov/periodicals/mcs2020/mcs2020-bauxite-alumina.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://pubs.usgs.gov/periodicals/mcs2020/mcs2020-bauxite-alumina.pdf |archive-date=2022-10-09 |url-status=live|access-date=29 June 2020|website=[[U.S. Geological Survey]]}}</ref> Increased [[aluminium recycling]], which requires less [[electric power]] than producing aluminium from ores, will considerably extend the world's bauxite reserves.

{{#section-h:List of countries by bauxite production|Data}}

{{notelist}}

==Processing==
[[File:CaboRojoDRBauxite.jpg|thumb|upright=1.3|Bauxite being loaded at Cabo Rojo, [[Dominican Republic]], to be shipped elsewhere for processing; 2007]]
[[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 [[surface mining|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]].<ref>{{Cite web|url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/periodictable/electrolysisrev3.shtml|title=BBC - GCSE Bitesize: Making aluminium|language=en-GB|access-date=2018-04-01|archive-url=https://web.archive.org/web/20180225224144/http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/periodictable/electrolysisrev3.shtml|archive-date=2018-02-25|url-status=dead}}</ref> Bauxite rocks are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical, and refractory.

Bauxite ore is usually 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]], [[Titanium dioxide|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]].<ref>{{cite web|url=http://www.worldwidewords.org/articles/aluminium.htm |title=Aluminium versus aluminum | author=Michael Quinion |publisher=Worldwidewords.org |date=2006-01-23 |access-date=2011-12-19}}</ref>

==Maritime safety==
As a [[bulk cargo]], bauxite is a Group A cargo that may liquefy if excessively moist.<ref>{{cite web|title=IMSBC CODE GROUP A CARGOES|url=https://www.bimco.org/cargo/solid-bulk-cargo/imsbc-code/imsbc-code-group-a-cargoes|access-date=21 November 2021|publisher=[[Baltic and International Maritime Council]]}}</ref> [[Liquefaction]] and the [[free surface effect]] can cause the cargo to shift rapidly inside the hold and make the ship unstable, potentially sinking the ship. One vessel suspected to have been sunk in this way was the [[MS Bulk Jupiter|MS ''Bulk Jupiter'']] in 2015.<ref>{{cite web|title=Bulk Jupiter sinking: A stark reminder of bauxite cargo risks|url=https://safety4sea.com/cm-bulk-jupiter-sinking-a-stark-reminder-of-bauxite-cargo-risks/|website=Safety4Sea|date=September 20, 2019|access-date=21 November 2021}}</ref> One method which can demonstrate this effect is the "can test", in which a sample of the material is placed in a cylindrical can and struck against a surface many times.<ref>{{cite web|title=What a Can Test Can Do|url=https://www.nepia.com/articles/what-a-can-test-can-do/|date=8 February 2021|access-date=21 November 2021}}</ref> If a moist [[slurry]] forms in the can, then there is a likelihood for the cargo to liquefy; although conversely, even if the sample remains dry it does not conclusively prove that it will remain that way, or that it is safe for loading.

==Source of gallium==
Bauxite is the main source of the rare metal [[gallium]].<ref>{{cite web|url=https://pubs.usgs.gov/of/2013/1272/pdf/ofr2013-1272.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://pubs.usgs.gov/of/2013/1272/pdf/ofr2013-1272.pdf |archive-date=2022-10-09 |url-status=live |title=Compilation of Gallium Resource Data for Bauxite Deposits Author: USGS |access-date=2017-12-01}}</ref>

During the processing of bauxite to [[Aluminium oxide|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 resin]].<ref name="Frenzel-2016">{{Cite journal|last1=Frenzel|first1=Max|last2=Ketris|first2=Marina P.|last3=Seifert|first3=Thomas|last4=Gutzmer|first4=Jens|date=March 2016|title=On the current and future availability of gallium|journal=Resources Policy|volume=47|pages=38–50|doi=10.1016/j.resourpol.2015.11.005}}</ref> 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.<ref name="Frenzel-2016" /> The remainder reports to the [[red mud]] and [[aluminium hydroxide]] streams.<ref name="Moskalyk">{{Cite journal|last=Moskalyk|first=R. R.|date=2003|title=Gallium: the backbone of the electronics industry|journal=Minerals Engineering|volume=16|issue=10|pages=921–929|doi=10.1016/j.mineng.2003.08.003}}</ref>

Bauxite is also a potential source for [[vanadium]].

==See also==
*[[Bauxite, Arkansas]]
*[[Rio Tinto Alcan]]
*[[United Company RUSAL]]
*[[MS Bulk Jupiter]]

==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 Bolkardaği bauxite deposits, Karaman, Turkey: Transformation from shale to bauxite''. Journal of Geochemical Exploration

==External links==
{{commons category|Bauxite}}
*[http://minerals.usgs.gov/minerals/pubs/commodity/bauxite/ USGS Minerals Information: Bauxite]
*[https://web.archive.org/web/20051003232659/http://www.mii.org/Minerals/photoal.html Mineral Information Institute]
*{{Cite NIE|wstitle=Bauxite |year=1905 |short=x}}

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[[Category:Sedimentary rocks]]
[[Category:Aluminium minerals]]
[[Category:Bauxite mining| ]]
[[Category:Articles containing video clips]]
[[Category:Regolith]]
[[Category:Weathering]]

Bauxite - Revision history

Ajay Kumar at 17:10, 24 August 2023