Cryolite is a fluoride of aluminum and sodium associated with granite. It is a valuable source of insoluble sodium used in frits and glazes. This material is a very active melter, because Cryolite lacks oxygen. It is useful in creating artificial reduction glazes for electric firing. Since this material is looking for oxygen to satisfy vacancies resulting from the gassing away of fluorine, it will take it from the kiln atmosphere or from neighboring molecules.