The main uses of fluoride, in terms of volume, are in the production of cryolite, NaAlF. It is used in aluminium smelting. Formerly, it was mined, but now it is derived from hydrogen fluoride. Fluorite is used on a large scale to separate slag in steel-making. Mined fluorite (CaF) is a commodity chemical used in steel-making.  Uranium hexafluoride is employed in the purification of uranium isotopes.