The role of cryolite is prominent in the electrical decomposition of alumina by the hall heroult method. The melting point of pure alumina is 2050°C. If a small amount of cryolite is added to the alumina, it begins to melt at low temperature (875°-900°C).
In the presence of cryolite the heat required for electrical decomposition is significantly reduced. And the cost of production comes down significantly. For this reason, the prices of aluminium were reduced considerably after the discovery of the hall heroult method The hall heroult method was discovered in 1885. In 1885 USA, the market price of aluminium was $ 100 per pound while in 1890 the market price of aluminium was $ 2 per pound.
Little Calcium fluoride(CaF2) can also be mixed with cryolite in alumina in the hall heroult method. Fluorspar (CaF2)also performs the same function as cryolite. That is, it reduces the melting point of the mixture and increases its electrical conductivity. In industrial processes, a mixture of 20 parts alumina, 60 parts cryolite and 20 parts CaF2 is often used.