16.36: Fluorite
- Page ID
- 4720
Fluorite | |
---|---|
Chemical composition | CaF2alcium 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) |
Figure \(\PageIndex{1}\): Fluorite with Barite and Galena
Elmwood Mine, Carthage, Tennessee
Figure \(\PageIndex{2}\): Fluorite with Sphalerite and Barite
Elmwood Mine, Carthage, Tennessee
Figure \(\PageIndex{3}\): Faceted purple fluorite
Figure \(\PageIndex{4}\): Green Fluorite
Westmoreland, New Hampshire
Figure \(\PageIndex{5}\): Faceted Green Fluorite; 229 carats
Figure \(\PageIndex{6}\): Fluorite
Figure \(\PageIndex{7}\): Yellow Fluorite Crystals
Clay Center, Ohio
Figure \(\PageIndex{8}\): Yellow Fluorite Faceted
847.4 carats and 84.7 carats
Figure \(\PageIndex{9}\): 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).