Kaolinite is the dominant clay mineral in china clay or kaolin along with some other
minerals of the same group namely dickite and nacrite, as well as halloisite. Kaolinite
originates from feldspar contained in different rocks, by weathering and the process is called
kaolinization. The alteration of feldspar takes place in two stages–first to montmorillonite
and then to kaolinite. Kaolin deposits may be either primary (in situ) or secondary
(transported), but the in situ deposits are more common. Chemically, the composition of pure
china clay is dominated by SiO2 in silicate form (47-50%), Al2O3 (34-37%) and water
showing as loss on ignition (10-12.5%). The chemical composition shows remarkable
consistency. In nature, small amounts of other constituents like free silica, mica, Fe2O3 , TiO2,
CaO, MgO, K2O and Na2O are invariably present – to a greater extent in primary deposits,
and to a lesser extent in secondary ones in which, part of these impurities are removed by
natural sorting. Production of modern whiteware commenced in India in the middle of 19th
century at Pathargatta in Bhagalpur district, Bihar.

The important uses are:

  1. Ceramics and glazes (non-refractory and refractory)
  2. Bone china
  3. Textile
  4. Paper
  5. Rubber
  6. Plastic
  7. Paint
  8. Pharmaceuticals and cosmetics
  9. Insecticide
  10. White cement
  11. Ink
  12. Ultramarine
  13. Synthetic zeolite
  14. Catalyst
  15. Soaps and detergents
  16. Fiber glass
  17. Explosives and pyrotechnics
  18. Adhesives and sealants