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What role does cryolite play in aluminum refining?

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A labeled diagram of the periodic table entry for fluorine, showing its atomic number 9, symbol F, atomic weight 18.998, electron configuration, and indicating it is a halogen and a gas at room temperature. — fluorine Properties of fluorine.

In the electrolytic production of aluminum, cryolite serves as a vital solvent and flux for alumina (aluminum oxide).12

In the Hall-Héroult process, alumina is dissolved in a molten bath consisting primarily of cryolite within reduction pots. This molten electrolyte allows the alumina to be reduced to metallic aluminum through the passage of a direct current between carbon anodes and a carbon cathode lining.32

Because cryolite is a rare mineral, the industry relies heavily on synthetic cryolite, which is manufactured using fluorine derived from fluorspar. During the smelting process, some fluoride from the cryolite is inevitably lost; consequently, aluminum fluoride is added periodically to the bath to maintain the necessary chemical composition and ensure maximum efficiency.123