Name the principal ore of aluminium. Explain the significance of leaching in the extraction of aluminium?

Aluminium is generally extracted from bauxite ore, this ore contains SiO2, iron oxides and titanium oxide as impurities. It is concentrated by digesting the powdered ore with a concentrated solution of NaOH at 473K and 35 atm pressure when Al2O3 gets leached out as sodium aluminate. The impurities are left behind.