Why is cryolite indispensable in aluminum electrolysis despite its scarcity?

Why is cryolite indispensable in aluminum electrolysis despite its scarcity?
Cryolite's role in aluminum smelting is foundational: it dissolves alumina and lowers the electrolysis temperature from over 2,000°C to roughly 950-1,000°C, making industrial aluminum production economically viable. Without it, direct electrolysis of molten alumina would require impossible furnace temperatures and container materials. The Hall-Heroult process, developed independently by Hall and Heroult in 1886, remains the only commercial method for aluminum production, and no substitute for cryolite has been found. Beyond its fluxing action, cryolite offers essential properties: it does not contain elements more electropositive than aluminum, remains stable under electrolysis conditions, does not volatilize or deliquesce, has a melting point above aluminum, and conducts electricity well. These characteristics reduce energy consumption and enable aluminum to settle at the cell bottom for easy extraction, making cryolite irreplaceable in modern smelting operations.