Flourite

Fluorite (also called fluorspar) is a halide mineral composed of calcium fluoride, CaF2. Crystal twinning is common and adds complexity to the observed crystal habits.
Fluorite is a colorful mineral, both in visible and ultraviolet light, and the stone has ornamental and lapidary uses,
Uses
1- fluorite is used as a flux for smelting.
2- in the production of certain glasses and enamels.
3- The purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, which is the intermediate source of most fluorine-containing fine chemicals.
4- Optically clear transparent fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration, making them valuable in microscopes and telescopes
5- Natural fluorite mineral has ornamental and lapidary uses.
6- Fluorite may be drilled into beads and used in jewelry,
7- Metallurgical grade fluorite (60–85% CaF2), the lowest of the three grades, has traditionally been used as a flux to lower the melting point of raw materials in steel production to aid the removal of impurities, and later in the production of aluminium.
8- Ceramic grade fluorite (85–95% CaF2) is used in the manufacture of opalescent glass, enamels and cooking utensils.
9- The highest grade, "acid grade fluorite" (97% or more CaF2), accounts for about 95% of fluorite consumption in the US where it is used to make hydrogen fluoride and hydrofluoric acid by reacting the fluorite with sulfuric acid.
10- acid-grade fluorite is also used in the production of AlF3 and cryolite (Na3AlF6), which are the main fluorine compounds used in aluminium smelting. Alumina is dissolved in a bath that consists primarily of molten Na3AlF6, AlF3, and fluorits to allow electrolytic recovery of aluminium.