krüoliit

Cryolite, chemical formula Na3AlF6, is a mineral composed of sodium, aluminum, and fluorine. In its natural state, it is a white or colorless crystalline solid, though impure samples can appear gray or reddish. Historically, cryolite was a relatively rare mineral, primarily found in Greenland. It gained significant industrial importance with the development of the Hall-Héroult process for producing aluminum.

The primary use of cryolite is as a solvent in the electrolytic production of aluminum. It dissolves aluminum oxide (alumina) at much lower temperatures than alumina alone, making the electrolysis process more energy-efficient and economically viable. Molten cryolite acts as the electrolyte, allowing for the reduction of aluminum oxide to molten aluminum metal. Without cryolite, the production of aluminum would be considerably more difficult and expensive.

While natural cryolite was once mined extensively, the demand has led to the widespread production of synthetic cryolite. This manufactured cryolite serves the same purpose in aluminum smelting. Beyond its major role in aluminum production, cryolite has had minor applications in the past, such as in the manufacture of enamels, white enamel paints, and as a flux in metallurgy. However, its use in these areas has largely been superseded by other materials. Due to its environmental impact and the availability of alternatives, its use has also been restricted or phased out in some applications, particularly in food additives where it was once used as a pesticide and in some countries as a food additive.