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Bauxite is a
sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentatio ...

sedimentary rock
with a relatively high
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
content. It is the world's main source of aluminium and
gallium Gallium is a with the  Ga and  31. Discovered by in 1875, Gallium is in of the periodic table and is similar to the other metals of the group (, , and ). Elemental gallium is a soft, silvery at . In its liquid state, it becomes ...

gallium
. Bauxite consists mostly of the aluminium
mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...

mineral
s
gibbsite Ball-and-stick model of the part of the crystal structure of gibbsite">crystal_structure.html" ;"title="Ball-and-stick model of the part of the crystal structure">Ball-and-stick model of the part of the crystal structure of gibbsite Gibbsite, A ...

gibbsite
(Al(OH)3),
boehmite Boehmite or böhmite is an aluminium oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminium ore bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. ...
(γ-AlO(OH)) and
diaspore Diaspore , also known as diasporite, empholite, kayserite, or tanatarite, is an aluminium oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombicIn crystallography, the orthorhombic crystal system is one of the 7 crystal systems. ...

diaspore
(α-AlO(OH)),
mixed
mixed
with the two
iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, ...

iron oxide
s
goethite Goethite () is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the "α" polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient tim ...

goethite
(FeO(OH)) and
haematite Hematite, also spelled as haematite, is a common iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of th ...
(Fe2O3), the aluminium
clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of involve them. They are important constitu ...
kaolinite Kaolinite ( ) is a clay mineral, with the chemical composition Aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedron, tetrahedral sheet of silica () ...

kaolinite
(Al2Si2O5(OH)4) and small amounts of
anatase Anatase is a metastable In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), mot ...
(TiO2) and
ilmenite Crystal structure of ilmenite Ilmenite, also known as manaccanite, is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. From a commercial perspective, ilmenite is the most important o ...
(FeTiO3 or FeO.TiO2). Bauxite appears dull in luster and is reddish-brown, white, or tan in color.

In 1821 the French people, French
geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, although backgrounds in physics, chemi ...

geologist
Pierre Berthier Pierre Berthier (; 3 July 1782, Nemours Nemours () is a commune A commune is an intentional community of people sharing living spaces, interests, values, beliefs, and often property Property (''latin: Res Privata'') in the Abstract an ...

Pierre Berthier
discovered bauxite near the village of
Les Baux
Les Baux
in
Provence Provence (, , , , ; oc, Provença or ''Prouvènço'' , ) is a geographical region and historical province of southeastern France, which extends from the left bank of the lower Rhône The Rhône ( , ; german: Rhone ; wae, Rotten ; it, R ...

Provence
, southern
France France (), officially the French Republic (french: link=no, République française), is a spanning and in the and the , and s. Its extends from the to the and from the to the and the ; overseas territories include in , in the N ...

France
.


Formation

Numerous classification schemes have been proposed for bauxite but, , there was no consensus. Vadász (1951) distinguished
lateritic Laterite is both a soil and a rock type rich in iron and aluminum and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by inten ...
bauxites (silicate bauxites) from
karst Karst is a topography Topography is the study of the forms and features of land surfaces. The topography of an area could refer to the surface forms and features themselves, or a description (especially their depiction in maps). Topography ...

karst
bauxite
ore ore – psilomelane Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese Manganese is a chemical element Image:Simple Periodic Table Chart- ...

ore
s (carbonate bauxites): * The carbonate bauxites occur predominantly in
Europe Europe is a which is also recognised as part of , located entirely in the and mostly in the . It comprises the westernmost peninsulas of the of Eurasia, it shares the continental landmass of with both and , and is bordered by the to the ...

Europe
,
Guyana Guyana ( or ), officially the Cooperative Republic of Guyana, is a country on the northern mainland of South America South America is a entirely in the and mostly in the , with a relatively small portion in the . It can also be ...

Guyana
,
Suriname Suriname (, sometimes spelled Surinam), officially known as the Republic of Suriname ( nl, Republiek Suriname ), is a country on the northeastern Atlantic coast of South America. Borders of Suriname, It is bordered by the Atlantic Ocean to the ...

Suriname
, and
Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of Hispanio ...

Jamaica
above
carbonate rock 250px, Carbonate ooids on the surface of a limestone; Carmel Formation (Middle Jurassic) of southern Utah, USA. Largest is 1.0 mm in diameter. Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major ...
s (
limestone Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its nat ...

limestone
and
dolomiteDolomite may refer to: *Dolomite (mineral) Dolomite () is an anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and ...
), where they were formed by lateritic
weathering Weathering is the deterioration of rocks In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology ...
and residual accumulation of intercalated
clay Clay is a type of fine-grained natural soil File:Stagnogley.JPG, Surface-water-Gley soil, gley developed in glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support ...

clay
layers – dispersed clays which were concentrated as the enclosing limestones gradually dissolved during
chemical weathering Weathering is the breaking down of rocks, soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive maps of ...
. * The lateritic bauxites are found mostly in the countries of the
tropics The tropics are the region of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% i ...

tropics
. They were formed by lateritization of various silicate rocks such as
granite Granite () is a coarse-grained (phaneritic A phanerite is an igneous rock Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...

granite
,
gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. Gneiss is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous Igneous rock (derived from the Latin Latin (, or ...

gneiss
,
basalt Basalt (, ) is a fine-grained extrusive A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope Extrusi ...

basalt
,
syenite Image:Nepheline-syenite-2005.jpg, Leucocratic variety of nepheline syenite from Sweden (särnaite) Syenite is a coarse-grained Intrusion, intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, ...

syenite
, and
shale Shale is a fine-grained, clastic of a clast (sand grain), derived from a basalt Basalt (, ) is a fine-grained extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ('' mafic '' lava) ...

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 Kaolinite ( ) is a clay mineral, with the chemical composition Aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedron, tetrahedral sheet of silica () ...

kaolinite
and the precipitation of the
gibbsite Ball-and-stick model of the part of the crystal structure of gibbsite">crystal_structure.html" ;"title="Ball-and-stick model of the part of the crystal structure">Ball-and-stick model of the part of the crystal structure of gibbsite Gibbsite, A ...

gibbsite
. Zones with highest aluminium content are frequently located below a
ferruginous The adjective ferruginous may mean: * Containing iron, applied to water, oil, and other non-metals * Having rust on the surface * With the rust (color) See also

* Ferrous, containing iron (for metals and alloys) or iron(II) cations * Ferric, co ...

ferruginous
surface layer. The
aluminium hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer Polymorphism (materials science), polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is Amphoteri ...

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 Cadmium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same nu ...

cadmium
, suggesting that the bauxite originates from recent
Miocene The Miocene ( ) is the first Epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; its name comes from the Greek words (', "less") and (', "new") and mean ...
ash Ash or ashes are the solid remnants of fire BBQ. Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. Fire is hot because th ...
deposits from episodes of significant volcanism in Central America.


Production and reserves

Australia is the largest producer of bauxite, followed by China. Increased
aluminium recyclingImage:Recycling-Code-41.svg, upAn aluminium recycling symbol. Aluminium recycling is the process by which scrap aluminium can be reused in products after its initial production. The process involves simply re-melting the metal, which is far less ex ...
, which has the advantage of lowering the cost in
electric power Electric power is the rate, per unit time, at which electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When used loosely, ''electrical energy'' refers to energy that has been conve ...
in producing aluminium, will considerably extend the world's bauxite reserves. In November 2010,
Nguyen Tan Dung Nguyễn is the most common Vietnamese name, Vietnamese family name. Outside of Vietnam, the surname is commonly rendered without diacritics as Nguyen. Nguyên is a different surname. By some estimates forty percent of Vietnamese people bear this ...

Nguyen Tan Dung
, the prime minister of
Vietnam Vietnam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,, group="n" is a country in Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is the ...

Vietnam
, announced that Vietnam's bauxite reserves might total 11,000 Mt (11 trillion kg); this would be the largest in the world.


Processing

Bauxite is usually because it is almost always found near the surface of the terrain, with little or no
overburden In mining, overburden (also called waste or spoil) is the material that lies above an area that lends itself to economical exploitation, such as the rock, soil, and ecosystem that lies above a coal seam or ore body. Overburden is distinct from tail ...
. , approximately 70% to 80% of the world's dry bauxite production is processed first into
alumina Aluminium oxide is a of and with the 23. It is the most commonly occurring of several , and specifically identified as aluminium(III) oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum depending on part ...

alumina
and then into aluminium by
electrolysis In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in ...

electrolysis
. 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 Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
solution at a temperature of . At these temperatures, the
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
is dissolved as
sodium aluminate Sodium aluminate is an inorganic In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, be ...
(the
Bayer processThe Bayer process is the principal industrial means of refining bauxite Bauxite is a sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic p ...
). The aluminium compounds in the bauxite may be present as
gibbsite Ball-and-stick model of the part of the crystal structure of gibbsite">crystal_structure.html" ;"title="Ball-and-stick model of the part of the crystal structure">Ball-and-stick model of the part of the crystal structure of gibbsite Gibbsite, A ...

gibbsite
(Al(OH)3),
boehmite Boehmite or böhmite is an aluminium oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminium ore bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. ...
(AlOOH) or
diaspore Diaspore , also known as diasporite, empholite, kayserite, or tanatarite, is an aluminium oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombicIn crystallography, the orthorhombic crystal system is one of the 7 crystal systems. ...

diaspore
(AlOOH); the different forms of the aluminium component will dictate the extraction conditions. The undissolved waste,
bauxite tailings Red mud, formally termed bauxite residue, is an industrial waste generated during the processing of bauxite into Aluminium oxide, alumina using the Bayer process. It is composed of various oxide compounds, including the iron oxides which give it ...
, after the aluminium compounds are extracted contains
iron oxides Iron oxides are chemical compounds composed of iron and oxygen. There are sixteen known iron oxides and oxyhydroxides, the best known of which is rust, a form of iron(III) oxide. Iron oxides and oxyhydroxides are widespread in nature and play an i ...

iron oxides
,
silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any su ...

silica
, calcia,
titania Titania may refer to: Astronomy * Titania (moon) Titania (), also designated Uranus III, is the largest of the moons of Uranus and the List of natural satellites by diameter, eighth largest moon in the Solar System at a diameter of . Discovere ...
and some un-reacted
alumina Aluminium oxide is a of and with the 23. It is the most commonly occurring of several , and specifically identified as aluminium(III) oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum depending on part ...

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 Aluminium oxide is a chemical compound of aluminium and oxygen with the chemical formula 23. It is the most commonly occurring of several Aluminium oxide (compounds), aluminium oxides, and specifically identified as aluminium(III) oxide. It is ...

aluminium oxide
, Al2O3, by heating in rotary kilns or fluid flash calciners to a temperature in excess of . This aluminium oxide is dissolved at a temperature of about in molten
cryolite Cryolite (Na3AlF6, sodium hexafluoroaluminate) is an uncommon mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crysta ...

cryolite
. Next, this molten substance can yield metallic aluminium by passing an
electric current An electric current is a stream of charged particle In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, ...
through it in the process of electrolysis, which is called the
Hall–Héroult process The Hall–Héroult process is the major industrial process Industrial processes are procedures involving chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add ...
, named after its American and French discoverers. Prior to the invention of this process, and prior to the
Deville process The Deville process was the first industrial process used to produce alumina Aluminium oxide is a chemical compound of aluminium and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It ...
, aluminium ore was refined by heating ore along with elemental
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
or
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
in a
vacuum A vacuum is a space Space is the boundless three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameter A parameter (from the Ancient Gree ...

vacuum
. The method was complicated and consumed materials that were themselves expensive at that time. This made early elemental aluminium more expensive than
gold Gold is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elemen ...

gold
.


Source of gallium

Bauxite is the main source of the rare metal
gallium Gallium is a with the  Ga and  31. Discovered by in 1875, Gallium is in of the periodic table and is similar to the other metals of the group (, , and ). Elemental gallium is a soft, silvery at . In its liquid state, it becomes ...

gallium
. During the processing of bauxite to
alumina Aluminium oxide is a of and with the 23. It is the most commonly occurring of several , and specifically identified as aluminium(III) oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum depending on part ...

alumina
in the
Bayer processThe Bayer process is the principal industrial means of refining bauxite Bauxite is a sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic p ...
, gallium accumulates in the
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
liquor. From this it can be extracted by a variety of methods. The most recent is the use of
ion-exchange resin An ion-exchange resin or ion-exchange polymer is a resin or polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tu ...
. 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 Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer Polymorphism (materials science), polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is Amphoteri ...

aluminium hydroxide
streams.


See also

*
Bauxite, Arkansas Bauxite is a city in Saline County, Arkansas, Saline County, Arkansas, United States. Located within Central Arkansas, the city is named for bauxite, the source ore for aluminum, which was found in abundant quantities in the area and became a source ...
*
Rio Tinto Alcan The aluminium division of Rio Tinto (previously known as Rio Tinto Alcan) is a subsidiary of Rio TintoRio Tinto, meaning "red river", may refer to: Businesses * Rio Tinto (corporation), an Anglo-Australian multinational mining and resources ...

Rio Tinto Alcan
*
United Company RUSAL United Company RUSAL, international public joint-stock company (russian: МКПАО «ОК РУСАЛ», MKPAO «ОК RUSAL») is the world's second largest aluminium Aluminium (aluminum in American English, American and Canadian English) is ...
* MS Bulk Jupiter


References


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. *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


USGS Minerals Information: Bauxite
* {{Authority control Sedimentary rocks Aluminium minerals Articles containing video clips Regolith Weathering