Kaolinite. Credit: Mineral Information Institute.

Kaolinite is the prototypical member of the kaolinite group of clay minerals. It consists of hexagonal flakes of composition Si4Al4O10(OH)8. It is formed by alteration of other clays or of feldspar and has triclinic system tabular crystals, clay-like masses, and particles. It is white with a dull luster and may be tinted by impurities. Hardness 2–2.5; relative density 2.6.


From kaolinite is made kaolin, or china clay, which is used for filling and coating paper, filling rubber and paints, and for making pottery and porcelain. Kaolin may also be used in the form of an oral suspension to treat chronic diarrhea, and in dusting powders and poultices.