Kaolinite - Wikipedia
It is raw kaolin that has been fired (in a rotary calcining kiln) high enough to remove the 12% (approx) crystal water. If you are a potter you can make your own calcined kaolin by simply bisque firing any raw powdered kaolin (in a small enough bisque vessel and slow enough ramp that the heat penetrates well).The kaolin purification process can be washed, calcined, magnetically selected, and the like. Washed kaolin production process. Washed kaolin is produced by coarsening, slurring, sieving, grinding, centrifuging, grading, chemical and possibly magnetic treatment, concentration and drying of coarse clay to achieve the desired purity, particle size and brightness.