MPPSC 2014 General Studies Solved Paper-1

(D) Bauxite, containing 15-25%aluminium, is the only ore that is used for commercial extraction of aluminium. It occurs mostly in the tropics, in horizontal layers normally beneath a few metres of overburden. The layers are usually mixed with various clay minerals, iron oxides and titanium dioxide. About 7% of the earth’s crust is aluminium,making it the third-most abundant element after oxygen and silicon.