Fluorite (Halide) 

Hardness: 4
Specific Gravity: 3.18

Characteristics: Purple, colorless, and a variety of other colors; perfect cleavage; vitreous luster; transparent to translucent; cubic or octahedral cleavage; insoluble in water and HCl; strongly fluorescent in ultraviolet light.

Found in dolostones; limestones; hydrothermal deposits; some felsic volcanics; some granitic and intermediate intrusives.

Fluorite is used as a decorative medium used in the fashioning such items as vases; as a flux in steel, ceramics, and glass; in the production of hydrofluoric acid which has various industrial uses.

(Primary text: Perkins, D. 2002. Mineralogy. Prentice Hall.)