Zircon
Zircon has been known since antiquity, albeit under various names. Today's name is most likely derived from the Persian language ("golden colored"). Because of its high refractive index and strong dispersion, it has great brilliance and intensive fire.
Zircons with the highest values in optical properties are designated as high zirons, those with the lowest values as low zircons. In between are the medium zircons.
| General Information |
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| Varieties/Types: | Hyacinth - Yellow-red to red-brown zircon. |
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| Chemical Formula | Michael O’Donoghue, Gems, Sixth Edition (2006) More from other references |
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| Zircon Treatments |
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| The brown varieties are heat-treated at temperatures of 1472-1832 degrees F (800-1000 degrees C), producing colorless and blue zircons. These colors do not necessarily remain constant; ultraviolet rays or sunlight can produce changes. - Gemstones of the world, Walter Schumann, 2001, p 108 |
| Synthetic Zircon |
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| Synthetic zircons are only of scientific interest. - Gemstones of the world, Walter Schumann, 2001, p 108 |
| Physical Properties of Zircon |
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| Mohs Hardness | 7.5Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Specific Gravity | 3.93 to 4.73Walter Schumann, Gemstones of the world (2001) More from other references |
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| Tenacity | BrittleHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Cleavage Quality | IndistinctWalter Schumann, Gemstones of the world (2001) More from other references |
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| Fracture | ConchoidalArthur Thomas, Gemstones (2009) |
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| Refractive Index | 1.810 to 2.024Walter Schumann, Gemstones of the world (2001) 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 | 0.045 to 0.059Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Pleochroism | Red zircon - distinct: purplish-red - reddish-brown; Orange/brown zircon - weak: yellow-brown - red-brown; Yellow - weak: honey-yellow - brown-yellow; Blue - strong: colorless to gray - blue; Green - weak: brownish-green - greenHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Dispersion |
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