China Clay, also known as Kaolin, is one of the finest clays, consisting primarily of the mineral kaolinite and typically generated when granite undergoes hydrothermal metamorphism. Kaolinite is a clay mineral that belongs to the industrial minerals group and has the chemical formula Al2Si2O5(OH)4. It's a stratified silicate mineral made up with one sublattice of silica (SiO4) and one octahedral sheet of alumina (AlO6) octahedra connected by oxygen molecules.

Kaolinite has a modest shrink–swell potential (1–15 meq/100 g) as well as a moderate cation-exchange potential. It's a mushy, muddy, generally white aggregate (dioctahedral phyllosilicate clay) formed by the chemical weathering of aluminium silicate minerals such as feldspar. Iron oxide colours it pink-orange-red in various areas worldwide, offering it a characteristic rust tint. White, yellow, or pale orange colours result from lower amounts. Kaolin is provided and shipped as a powder form, semi-dry vermicelli, or fluid slush in industrial levels.