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Layered non-swelling aluminosilicate 1:1 clay mineral / From Wikipedia, the free encyclopedia

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Kaolinite (/ˈk.ələˌnt, -lɪ-/ KAY-ə-lə-nyte, -lih-)[5][6][7] is a clay mineral, with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica (SiO4) linked through oxygen atoms to one octahedral sheet of alumina (AlO6) octahedra.[8]

Quick facts: Kaolinite, General, Category, Formula .mw-par...
Kaolinite-serpentine group
(repeating unit)
Al2Si2O5(OH)4, or in oxide notation: Al2O3·2SiO2·2H2O
IMA symbolKln[1]
Strunz classification9.ED.05
Crystal systemTriclinic
Crystal classPedial (1)
(same H-M symbol)
Space groupP1
Unit cella = 5.13 Å, b = 8.89 Å
c = 7.25 Å; α = 90°
β = 104.5°, γ = 89.8°; Z = 2
ColorWhite to cream, sometimes red, blue or brown tints from impurities and pale-yellow; also often stained various hues, tans and browns being common.
Crystal habitRarely as crystals, thin plates or stacked. More commonly as microscopic pseudohexagonal plates and clusters of plates, aggregated into compact, claylike masses
CleavagePerfect on {001}
TenacityFlexible but inelastic
Mohs scale hardness2–2.5
LusterPearly to dull earthy
Specific gravity2.16–2.68
Optical propertiesBiaxial (–)
Refractive indexnα = 1.553–1.565,
nβ = 1.559–1.569,
nγ = 1.569–1.570
2V angleMeasured: 24° to 50°, Calculated: 44°
Quick facts: Kaolinite, Traditional Chinese, Simplifi...
Traditional Chinese高嶺石
Simplified Chinese高岭石
Literal meaning"Gaoling stone"

Kaolinite is a soft, earthy, usually white, mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminium silicate minerals like feldspar. It has a low shrink–swell capacity and a low cation-exchange capacity (1–15 meq/100 g).

Rocks that are rich in kaolinite, and halloysite, are known as kaolin (/ˈk.əlɪn/) or china clay.[9] In many parts of the world kaolin is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lower concentrations yield white, yellow, or light orange colors. Alternating layers are sometimes found, as at Providence Canyon State Park in Georgia, United States.

Kaolin is an important raw material in many industries and applications. Commercial grades of kaolin are supplied and transported as powder, lumps, semi-dried noodle or slurry. Global production of kaolin in 2021 was estimated to be 45 million tonnes, [10] with a total market value of $US4.24 billion.[11]