Difference between revisions of "Fluorite"
From The Gemology Project
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[[Image:fluorite.JPG|left|framed|Fluorite]]<br clear="left" /> | [[Image:fluorite.JPG|left|framed|Fluorite]]<br clear="left" /> | ||
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− | + | [[image:Yellow_fluorite.jpg|left|thumb|200px|Yellow Fluorite Crystals <br /> Clay Center, Ohio]] | |
+ | [[image:Yellow_faceted_fluorite.jpg|left|200px|Yellow Fluorite]] | ||
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==Diagnostics== | ==Diagnostics== | ||
Revision as of 14:01, 26 September 2010
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) |
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).