What is the significance of leaching in the extraction of aluminium?

The method of leaching consists of treating the powdered ore with a suitable reagent which can selectively dissolve the ore but not the impurities. The impurities are filtered out and are recovered from the solution. For example, bauxite ore containing SiO2, iron oxide, and titanium oxides impurities are concentrated by this method. Leaching is significant as it helps in removing the impurities like SiO2, FeO2, TiO¬2, etc from the bauxite ore.