kaolin

Also known as porcelain clay, china clay, kaolinite clay, paper clay, lithomarge, lithomarga, kao-lin, gaoling

clay rich in kaolinite

Key facts

Category: Phyllosilicate minerals
Group: Kaolinite- Serpentine group, kaolinite subgroup
Formula: Al 2 Si 2 O 5 (OH) 4 , or in oxide notation: Al 2 O 3 · 2SiO 2 · 2H 2 O
Ima symbol: Kln
Strunz classification: 9.ED.05
Crystal system: Triclinic
Crystal class: Pedial (1) , (same H-M symbol )
Space group: P 1
Unit cell: a = 5.13 Å , b = 8.89 Å , c = 7.25 Å; α = 90° , β = 104.5°, γ = 89.8°; Z = 2
Color: White to cream, sometimes red, blue or brown tints from impurities and pale-yellow; also often stained various hues, tans and browns being common.
Crystal habit: Rarely as crystals, thin plates or stacked. More commonly as microscopic pseudohexagonal plates and clusters of plates, aggregated into compact, claylike masses.
Cleavage: Perfect on {001}
Tenacity: Flexible but inelastic
Mohs scale hardness: 2–2.5
Luster: Pearly to dull earthy
Streak: White
Specific gravity: 2.16–2.68
Optical properties: Biaxial (–)

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Wikidata facts

Image: Kütahya City Museum 9116.jpg

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Commons category: Kaolin

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Article

Kaolinite (/ˈkeɪ.ələˌnaɪt, -lɪ-/ KAY-ə-lə-nyte, -⁠lih-; also called kaolin) is a clay mineral, with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one "tetrahedral" sheet of silicate tetrahedra (SiO4) linked to one "octahedral" sheet of aluminate octahedrons (AlO2(OH)4) through oxygen atoms on one side, and another such sheet through hydrogen bonds on the other side.

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).