Fluorite

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Rectangle fluorite
34.78 carats
© Rarestone.com

The word Fluorite derived from the Latin "fluo" - to flow, because the mineral is used as a flux in iron smelting.

Fluorites from certain localities exhibit a very strong fluorescence, due to impurities in the crystal. In 1852 the phenomenon of fluorescence was named after fluorite. It also gave the name to its constitutive element fluorine.

Fluorite has a wide range of colours, which depends on impurities, exposure to radiation, and the size of the colour centers. Colour distribution is often zonal or spotty.

Fluorite can be used in jewelry, cut into beads. But it is not widely used as a semiprecious stone because of its low hardness.

Fluorite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 
 
 
 
 
 
 
 

Fluorite Gemstones by Size

This table shows distribution of Fluorite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.21 cts
Heaviest:450 cts
Average:36.63 cts
Total photos:61
Do you have a larger Fluorite? Why not upload a photo?
0.21ct to 45.19ct45.19ct to 90.17ct90.17ct to 135.15ct135.15ct to 180.13ct180.13ct to 225.11ct225.11ct to 270.08ct270.08ct to 315.06ct315.06ct to 360.04ct360.04ct to 405.02ct405.02ct to 450.00ct
General Information
Varieties/Types:
Blue John - A banded white/purple variety of Fluorite from England.
Other Names/Trade Names:
Chemical Formula
CaF
 
2
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Photos of natural/un-cut material from mindat.org
Fluorite Treatments
The blue to deep blue to black color seen in some fluorites is derived from a color center, the F-center. This involves an electron-center precursor, and a missing fluorine atom in the fluorite, CaF2. An electron liberated by irradiation or other processes (Nassau, 1983) from a hole-center precursor can be trapped at the fluorine vacancy to become the electron color-center. Many other color-centers are known in fluorite, including those producing yellow, green, violet, pink, and other colors; some of these are stable to light, others are not.
The color of most of these color centers can be lightened by a gentle heating to 100-150°C and is totally removed at 200-300°C. This process has long been used to lighten some excessively dark blue john, a deep blue, banded massive fluorite found in Derbyshire, England, and used for carved ornamental objects.
Although colored impregnation and dyeing do not seem to have been reported, their use on massive fluorite would not be too surprising. Plastic impregnation is detected by careful examination; the heat and irradiation treatments are not identifiable - Nassau (1984)

Artificial irradiation of some colorless to pale green fluorite produces a typical "iolite blue", "tanzanite", "purplish-blue", also dark blue, dark green and bright purple - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 9
Synthetic Fluorite
Synthetic fluorite in all colours is known. - Gemstones of the world, Walter Schumann, 2001, p 198
Physical Properties of Fluorite
Mohs Hardness4 to 0
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Specific Gravity3.00 to 3.25
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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TenacityBrittle
Arthur Thomas, Gemstones (2009)
Cleavage QualityPerfect
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Perfect and easyMore from other references
FractureConchoidal
Walter Schumann, Gemstones of the world (2001)
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Optical Properties of Fluorite
Refractive Index1.432 to 1.436
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterIsotropic
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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BirefringenceNone
Walter Schumann, Gemstones of the world (2001)
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
Dispersion0.007
Walter Schumann, Gemstones of the world (2001)
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Colour
Colour (General)Colourless, pink, red, brown, green, yellow, blue, violet. Colour change: blue/violet, smoky brown/lilac
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Colour (Daylight)Smoky-brown (from India)
Michael O’Donoghue, Gems, Sixth Edition (2006)
Colour (Incandescent Light)Mauve (from India)
Michael O’Donoghue, Gems, Sixth Edition (2006)
Causes of ColourViolet, Mie scattering on calcium microcrystallites. Blue Y3+ + F vacancy +2 electrons. "Emerald" green ("chrome fluorite"), Sm2+. Yellowish green, color center containing Y3+ and Ce associated with an F vacancy. Yellow, O3 color center = O2 substituting for fluorite. Pink, YO2 color center (Y3 + O3-2). Color change, Y3+ associated color center and Sm2+, with minor influence of a Ce3+ associated color center
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreVitreous
Arthur Thomas, Gemstones (2009)
Fluorescence & other light emissions
Fluorescence (General)Commonly blue to violet or green
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Fluorescence (Long-Wave UV)Inert to strong blue to green
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
PhosphorescenceSome specimens phosphoresce
Michael O’Donoghue, Gems, Sixth Edition (2006)
TriboluminescenceMay show triboluminescence
Michael O’Donoghue, Gems, Sixth Edition (2006)
ThermoluminescenceMay show thermoluminescence
Michael O’Donoghue, Gems, Sixth Edition (2006)
Crystallography of Fluorite
Crystal SystemIsometric
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
HabitCubic, massive
Arthur Thomas, Gemstones (2009)
Geological Environment
Where found:Fluorite occurs in low-to-high temperature hydrothermal veins, granites and granite pegmatites
Michael O’Donoghue, Gems, Sixth Edition (2006)
Inclusions in Fluorite
Negative crystals, two- or three-phase inclusions, healing cracks, crystal inclusions - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 1
Further Information
Mineral information:Fluorite information at mindat.org
Significant Gem Localities
France
 
  • Auvergne-Rhône-Alpes
    • Haute-Savoie
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 412
Myanmar
 
  • Mandalay Region (Mandalay Division)
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Kyatpyin North
Ted Themelis (2008) Gems & mines of Mogok
        • Kyauk-Pyat-That
Ted Themelis (2008) Gems & mines of Mogok
        • Pein-Pyit (Painpyit; Pyan Pyit)
Ted Themelis (2008) Gems & mines of Mogok
    • Yamethin District
Ted Themelis (2008) Gems & mines of Mogok
Peru
 
  • Ancash Department
    • Bolognesi Province
      • Huallanca District
        • Huallanca
    • Pallasca Province
      • Pampas District
  • Pasco department
    • Pasco province
      • Huayllay district
        • Huaron mining district
UK
 
  • England
    • Co. Durham
      • North Pennines
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 412
          • Frosterley
            • Rogerley Quarry
Fisher, J.E., and L. Greenbank, 2000, The Rogerley Mine, Weardale, County Durham, England. Rocks and Minerals, 75(1), 54-61.
    • Derbyshire
      • Castleton
[var: Blue John] [www.thamesvalleyminerals.com]
[var: Blue John] Fluorite: The Collector's Choice. Extra Lapis English No. 9
USA
 
  • Illinois
    • Hardin Co.
      • Cave-in-Rock Sub-District
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 412
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