Kaolinite is a mineral with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen molecules to one octahedral sheet of alumina octahedra. It is also known as china clay and kaolin (高嶺土 in pinyin: gao1 ling3 tu3), named after Gaoling (“High Hill”), Jingde Town, Jiangxi, China.

It is a soft, earthy, usually white mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of 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 a yellow or light orange colour. 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 in Brazil, France, Britain, Germany, India, Australia, Japan (Amakusa), 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, paper, as a food additive, in toothpaste, 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.

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