| General Information |
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| Chemical Formula | Michael O’Donoghue, Gems, Sixth Edition (2006) More from other references |
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| Physical Properties of Willemite |
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| Mohs Hardness | 5.5Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Specific Gravity | 3.89 to 4.18Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Cleavage Quality | DistinctArthur Thomas, Gemstones (2009) |
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| Fracture | Sub-ConchoidalArthur Thomas, Gemstones (2009) |
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| Optical Properties of Willemite |
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| Refractive Index | 1.687 to 1.723Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Optical Character | Uniaxial/+Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Birefringence | 0.028 to 0.030Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Pleochroism | NilArthur Thomas, Gemstones (2009) |
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| Dispersion | LowArthur Thomas, Gemstones (2009) |
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| Chatoyancy | RareHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Colour |
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| Colour (General) | Colourless, yellow, greenish-yellow, yellow-green, orange, brown, red, blueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Causes of Colour | Yellow, Mn2+ in tetrahedral coordinationW. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) |
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| Transparency | Transparent,Translucent,OpaqueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Lustre | ResinousHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Fluorescence & other light emissions |
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| Fluorescence (General) | Weak to strong green-(yellow), common phosphorescenceHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Fluorescence (Short Wave UV) | Shows an intense green fluorescence – some specimens may also show green phosphorescenceMichael O’Donoghue, Gems, Sixth Edition (2006) |
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| Crystallography of Willemite |
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| Crystal System | TrigonalHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Habit | Prismatic, massiveMichael O’Donoghue, Gems, Sixth Edition (2006) More from other references |
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| Geological Environment |
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| Where found: | Willemite occurs in zinc deposits in limestones and is an uncommon ore of zinc.Michael O’Donoghue, Gems, Sixth Edition (2006) |
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| Further Information |
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| Mineral information: | Willemite information at mindat.org |
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| Significant Gem Localities |
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| Namibia | | |
| [MinRec 12:45, 8:Tsumeb 34/50/67] |
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