Aluminium is extracted from alumina (${\text{Al}}_2{\text{O}}_3$) by electrolysis of a molten mixture of:

In the Hall-Heroult process, pure alumina (${\text{Al}}_2{\text{O}}_3$) is mixed with cryolite (${\text{Na}}_3{\text{AlF}}_6$) and fluorspar (${\text{CaF}}_2$).Cryolite and fluorspar lower the melting point of the mixture from about $2323\text{K}$ to $1173\text{K}$.They also increase the electrical conductivity of the molten mass.