cement

Kaolin is the main type of clay in porcelain. Bone china is a porcelain body that has an inclusion of bone ash, calcined animal bone (calcium phosphate), which adds hardness and translucency.

calcium

calcined alumina is Al2O3 and alumina hydrate is Al2O3. 3H2O. It's difference in the molecule structure.

Natural Cancained clay is used for making refractory bricks and shapes.But it find best and cheap use in the boiler of thermal power plants as a bed material. Because here it does not required any benification or calcination. you have to only to make grains (iron free) of required sizes which is directly used in the boiler of a thermal power plant as a bed material