Kaolinite Wikipedia. Kaolinite k e l n a t is a clay mineral part of the group of industrial minerals with the chemical composition al 2 si 2 o 5 is a layered silie mineral with one tetrahedral sheet of silica sio 4 linked through oxygen atoms to one octahedral sheet of alumina alo 6 octahedra rocks that are rich in kaolinite are known as kaolin k e l n or china clay