Kryoliitti

Kryoliitti, also known as cryolite, is a rare, naturally occurring mineral composed primarily of sodium hexafluoroaluminate (Na₃AlF₆). It is a colorless to white crystalline compound that often appears as transparent to translucent masses. Kryoliitti is notable for its high solubility in water and its role in industrial processes, particularly in the production of aluminum.

The mineral was first discovered in 1799 in Ivittuut, a small village in southwestern Greenland, where it was historically mined. The name "cryolite" derives from the Greek words *kryos* (meaning "cold") and *lithos* (meaning "stone"), referencing its occurrence in icy regions. Kryoliitti was later synthesized in the laboratory, leading to its widespread use in industry despite its scarcity in nature.

Kryoliitti serves as a crucial flux in the Hall–Héroult process, the primary industrial method for producing aluminum from alumina (aluminum oxide). By lowering the melting point of alumina, cryolite facilitates the electrolysis of aluminum oxide, making the extraction process more energy-efficient. Historically, natural cryolite was the primary source, but synthetic cryolite is now predominantly used due to its lower cost and greater availability.

Beyond aluminum production, cryolite has applications in the manufacture of optical glasses, as a flux in welding, and in certain chemical processes. Its unique properties, such as high thermal stability and electrical conductivity, contribute to its industrial utility. However, due to environmental concerns and the development of synthetic alternatives, natural cryolite mining has declined significantly in recent decades. The Ivittuut mine, once the world’s largest cryolite source, closed in 1987, leaving synthetic production as the dominant method.