Aluminium refining is conducted primarily through the Bayer Process, which involves the separation of aluminium oxide from the iron oxide in bauxite. Under the Bayer Process, which was developed by Karl Joseph Bayer in 1888, the aluminium-bearing minerals in bauxite - Gibbsite, Böhmite and Diaspore - are selectively extracted from the insoluble components (mostly oxides) by dissolving them in a solution of sodium hydroxide.

Gibbsite:

Böhmite and Diaspore:

Aluminium oxide precipitates when aluminium hydroxide is introduced to the liquid sodium aluminate. The crystals of aluminium oxide are washed and heated to get rid of the water. This results in a fine white powder (aluminium oxide) also known as alumina.