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16.36: Fluorite

  • Page ID
    4720
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    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)

     

    File:Fluorite barite galena.jpg

    Figure \(\PageIndex{1}\): Fluorite with Barite and Galena 
    Elmwood Mine, Carthage, Tennessee

     

    File:Fluorite sphalerite barite.jpg

    Figure \(\PageIndex{2}\): Fluorite with Sphalerite and Barite 
    Elmwood Mine, Carthage, Tennessee

     

    File:Faceted fluorite.jpg

    Figure \(\PageIndex{3}\): Faceted purple fluorite                                                

     

     

    File:Green fluorite massive.jpg

    Figure \(\PageIndex{4}\): Green Fluorite
    Westmoreland, New Hampshire

     

    Figure \(\PageIndex{5}\): Faceted Green Fluorite; 229 carats

     

    Figure \(\PageIndex{6}\): Fluorite

     

     

    File:Yellow fluorite.jpg

    Figure \(\PageIndex{7}\): Yellow Fluorite Crystals 
    Clay Center, Ohio

     

    Figure \(\PageIndex{8}\): Yellow Fluorite Faceted 
    847.4 carats and 84.7 carats

     

    File:Green fluor facet.jpg

    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).