Claim: Cryolite, first described in 1798 by Danish veterinarian and physician Peder Christian Ablidgaard, was historically used as an ore of aluminum but is used as an insecticide and a pesticide and is used in fireworks.
Evidence: Cryolite (Na3AlF6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, depleted by 1987. Cryolite was first described in 1798 by Danish veterinarian and physician Peder Christian Abildgaard (1740–1801); it was obtained from a deposit of it in Ivigtut and nearby Arsuk Fjord, Southwest Greenland. It was historically used as an ore of aluminium and later in the electrolytic processing of the aluminium-rich oxide ore bauxite (itself a combination of aluminium oxide minerals such as gibbsite, boehmite and diaspore). Molten cryolite is used as a solvent for aluminium oxide (Al2O3) in the Hall–Héroult process, used in the refining of aluminium. Cryolite is used as an insecticide and a pesticide. It is also used to give fireworks a yellow color.