How is aluminum made from its ore?

Aluminum is abundant in rocks, but it is strongly bound to other elements rather than usually occurring as free metal. Primary production begins with bauxite, an ore containing aluminum-bearing minerals. Chemical refining separates much of the unwanted material and produces alumina, aluminum oxide. Alumina remains a compound; it is not aluminum metal.

The Hall–Héroult process converts alumina to metal using electrical energy. Alumina is dissolved in a molten cryolite-based mixture that conducts through mobile ions. This is a molten electrolyte, not an aqueous solution. Cryolite helps provide a workable liquid medium without requiring pure alumina itself to be the molten bath.

A direct electrical current drives reduction at the negative cathode: aluminum-bearing ions gain electrons and form liquid aluminum. The metal collects at the bottom above the carbon-lined cathode. At the positive carbon anodes, oxygen-bearing species participate in reactions that consume the carbon and produce mainly carbon dioxide. The anodes are therefore reactants as well as electrical conductors.

An ideal overall balance is 2Al₂O₃ + 3C → 4Al + 3CO₂. Aluminum, oxygen and carbon atoms are conserved, while electrical energy drives the separation. Real cells also have side reactions and require heat and emissions management. The collected metal is later cast and may be alloyed; recycling existing aluminum instead avoids repeating the extraction from alumina.