Kaolinite

Kaolinite ( KAY-ə-lə-nyte, -⁠lih-; also called kaolin) is a clay mineral, having 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 linked 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). Rocks that are rich in kaolinite, and halloysite, are known as kaolin () or china clay. In many parts of the world, kaolin is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lower concentrations of iron oxide yield white, yellow, or light orange colors of kaolin. Alternating lighter and darker 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, with a total market value of US $4.24 billion.