''Kaolin redirects here. For the band, see Kaolin (band).

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- align=center bgcolor="#9966FF" Kaolinite

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- align=center

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- align=center bgcolor="#9966FF" General

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- CategoryMineral

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- Chemical formulaAl₂Si₂O₅(OH)₄

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- align="center" bgcolor="#9966FF" Identification

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- Colour White, sometimes red, blue or brown tints from impurities

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- Crystal system triclinic

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- Cleavage perfect on {001}

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- Mohs Scale hardness 2 - 2.5

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- Luster dull and earthy

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- Refractive index α 1.553 - 1.565, β 1.559 - 1.569, γ 1.569 - 1.570

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- Specific gravity 2.16 - 2.68

Kaolinite is a clay mineral with the chemical composition Al₂Si₂O₅(OH)₄. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra. Rocks that are rich in kaolinite are known as china clay or kaolin (), named after Gaoling ("High Hill") in Jingde Town, Jiangxi, China. It was first described as a mineral species in 1867 for an occurrence in the Jari River basin of Brazil.^*

Kaolinite has a low shrink-swell capacity and a low cation exchange capacity (1-15 meq/100g.)

It is a soft, earthy, usually white mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminium silicate minerals like feldspar. In many parts of the world, it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow or light orange colours. Alternating layers are sometimes found, as at Providence Canyon State Park in Georgia, USA.

Kaolinite is one of the most common minerals; it is mined, as kaolin, in Brazil, France, Britain, Germany, India, Australia, Japan , China, and the southeastern U.S. states of Georgia, Florida, and, to a lesser extent, South Carolina. Due to its extremely fine nature (finer than silt), it is mixed with water and transported in tanks as a liquid slurry. It is used in ceramics, medicine, bricks, coated paper, as a food additive, in toothpaste, as a light diffusing material in white incandescent light bulbs, and in cosmetics. A recent use is as a specially formulated spray applied to fruits, vegetables, and other vegetation to repel or deter insect damage. A traditional use is to soothe an upset stomach, similar to the way parrots (and later, humans) in South America originally use it, and until 2003, it was the active substance of Kaopectate. The largest use is in the production of paper, as it is a key ingredient in creating "glossy" paper (but calcium carbonate, an alternative material, is competing in this function).

Natural kaolinite usually contains small amounts of uranium and thorium, and is therefore useful in radiological dating. While a single magazine made using kaolinite does not contain enough radioactive material to be detected by a security-oriented monitor, this does result in truckloads of high end glossy paper occasionally tripping an overly-sensitive radiation monitor.

The crystallography of kaolinite played a role in Linus Pauling's work on the nature of the chemical bond.

See also

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• List of minerals
• Porcelain
• Paper

References

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• Deer, W. A., Howie, R. A., and Zussman, J. (1992). An introduction to the rock-forming minerals (2nd ed.). Harlow: Longman ISBN 0-582-30094-0
• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy - after J. D. Dana, 20th ed., Wiley, pp. 428 - 429, ISBN 0471805807
• The Mineral KAOLINITE - Mineral Galleries
• Evolutionary biology: Dirty eating for healthy living by Jared M. Diamond
• Mindat
• Webmineral data
• MSDS: Incandescent Light Bulb - GE

Phyllosilicates | Aluminium minerals | Hydroxide minerals

Каолин | Caolí | Kaolin | Kaolinit | Kaolin (géologie) | Caolino | Pri gwynn | Kaolien | カオリナイト | Kaolinit | Каолинит | Kaolinit | Каолинит | Kaoliini | Kaolin | Kaolin