kaolinite

{{Infobox mineral | name = Kaolinite | category = Phyllosilicate minerals | group = Kaolinite-Serpentine group, kaolinite subgroup | boxwidth = | image = Kaolinite from Twiggs County in Georgia in USA.jpg |imagesize=210px| alt = | caption = | formula = , or in oxide notation: | IMAsymbol = Kln | strunz = 9.ED.05 | system = Triclinic | class = Pedial (1) (same H-M symbol) | symmetry = P1 | 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. | habit = Rarely as crystals, thin plates or stacked. More commonly as microscopic pseudohexagonal plates and clusters of plates, aggregated into compact, claylike masses. | twinning = | cleavage = Perfect on {001} | fracture = | tenacity = Flexible but inelastic | mohs = 2–2.5 | luster = Pearly to dull earthy | refractive = nα = 1.553–1.565, nβ = 1.559–1.569, nγ = 1.569–1.570 | opticalprop = Biaxial (–) | pleochroism = | 2V = Measured: 24° to 50°, Calculated: 44° | streak = White | gravity = 2.16–2.68 | melt = | fusibility = | diagnostic = | solubility = | references = }} Kaolinite ( ; 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 () linked to one "octahedral" sheet of aluminate octahedrons () 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).