Willemite

Big Photo

Tsumeb, Oshikoto Region, Namibia
4.89 carats
© irocks.com

Willemite was discovered in 1830 and named after William I, King of the Netherlands.

Willemite is famous for its remarkable luminescent properties. It exhibits strong green fluorescence under short-wave ultraviolet light. Some specimens may exhibit phosphorescence, they continue to glow for some time even after the UV source is removed.

Gem quality crystals are usually small and rarely exceed two grams, but can be faceted into attractive gems.

Willemite Gemstones by Colour

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

Willemite Gemstones by Size

This table shows distribution of Willemite 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:0.19 cts
Heaviest:4.89 cts
Average:1.47 cts
Total photos:16
Do you have a larger Willemite? Why not upload a photo?
0.19ct to 0.66ct0.66ct to 1.13ct1.13ct to 1.60ct1.60ct to 2.07ct2.07ct to 2.54ct2.54ct to 3.01ct3.01ct to 3.48ct3.48ct to 3.95ct3.95ct to 4.42ct4.42ct to 4.89ct
General Information
Chemical Formula
Zn
 
2
SiO
 
4
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Photos of natural/un-cut material from mindat.org
Physical Properties of Willemite
Mohs Hardness5.5
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Specific Gravity3.89 to 4.18
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Cleavage QualityDistinct
Arthur Thomas, Gemstones (2009)
FractureSub-Conchoidal
Arthur Thomas, Gemstones (2009)
Optical Properties of Willemite
Refractive Index1.687 to 1.723
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterUniaxial/+
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.028 to 0.030
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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PleochroismNil
Arthur Thomas, Gemstones (2009)
DispersionLow
Arthur Thomas, Gemstones (2009)
ChatoyancyRare
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Colour
Colour (General)Colourless, yellow, greenish-yellow, yellow-green, orange, brown, red, blue
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Causes of ColourYellow, Mn2+ in tetrahedral coordination
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreResinous
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Fluorescence & other light emissions
Fluorescence (General)Weak to strong green-(yellow), common phosphorescence
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Fluorescence (Short Wave UV)Shows an intense green fluorescence – some specimens may also show green phosphorescence
Michael O’Donoghue, Gems, Sixth Edition (2006)
Crystallography of Willemite
Crystal SystemTrigonal
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
HabitPrismatic, massive
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Geological Environment
Where found:Willemite occurs in zinc deposits in limestones and is an uncommon ore of zinc.
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Further Information
Mineral information:Willemite information at mindat.org
Significant Gem Localities
Canada
 
  • Québec
    • Montérégie
      • La Vallée-du-Richelieu RCM
        • Mont Saint-Hilaire
Namibia
 
  • Oshikoto Region
    • Tsumeb
[MinRec 12:45, 8:Tsumeb 34/50/67]
USA
 
  • New Jersey
    • Sussex Co.
      • Franklin Mining District
        • Ogdensburg
          • Sterling Hill
Copyright © Jolyon & Katya Ralph 1993-2019. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.