Calcium carbonate

is a chemical compound with the formula CaCO3. It is a common substance found in rocks as the mineral scalcite and aragonite (most notably as limestone, which contains both of those minerals...

Bauxite

an aluminium ore, is the World ̍ s main source of aluminium. It consists mostiy of the diaspore ( α - ALO(OH)3) , boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite and haematite, the clay mineral kaolinite and small amounts...