What is the role of cryllite in the metallurgy of aluminimum?

Aluminium metal is obtained by the electrolytic reduction of alumina (Hall- Heroult process). The melting point of pure alumina is very high (2323K). Cryolite $\left(N{a}_{3}AI{F}_6\right)$ and / or fluorspar $\left(Ca{F}_2\right)$ is added to alumina because

(i) it lowers the melting point of the mixture (from 2323 K to 1140 K).
(ii) it also makes it a better conductor of electricity of $A{l}_2{O}_3$.