Fluorite

Fluorite
Chemical composition	CaF2 Calcium fluoride
Crystal system	Cubic
Habit	Octahedral, cubes, interpenetrant twins
Cleavage	Perfect, octahedral
Fracture	Conchoidal
Hardness	4
Optic nature	Isotropic
Refractive index	1.434
Birefringence	Isotropic
Dispersion	Very low, 0.007
Specific gravity	3.18
Lustre	Poor vitreous
Fluorescence	Bluish-white, purple (LW)

Fluorite with Barite and Galena
Elmwood Mine, Carthrage, Tennessee

Fluorite with Sphalerite and Barite
Elmwood Mine, Carthrage, Tennessee

Faceted purple fluorite

Green Fluorite
Westmoreland, New Hampshire

Faceted Green Fluorite; 229 carats

Fluorite

Yellow Fluorite Crystals
Clay Center, Ohio

Yellow Fluorite Faceted
847.4 carats and 84.7 carats

Yellowish Green Fluorite

Diagnostics

Thermoluminescence

Fluorite may luminesce when heated. The stored energy from UV radiation is released if heated to a certain temperature and the effect depends on the amount of stored energy.
One can see this when a small amount of fluorite is placed on a teaspoon and heated over a candle for a few minutes (in a dark room).
Material from Telemark, Norway will show a blue-green thermoluminescence.

Optical phenomena

Color change

Color change fluorite has been reported with a change from blue to purple (much like some color change garnet).