Kyanite (Cyprine)
Nepal
3.03 carats
© Mineral Classics
Kyanite is named after Greek word for "blue", because of its colour. Some fine specimens have sapphire-blue colour with violet pleochroism.
Kyanite has a wide variations of hardness in the same crystal depending on direction (across or along axes). It complicates the cutting of this material.
Cut stones reach 10 - 15 carats. Varieties with alexandrite effect and cat's eye are known.
General Information |
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Other Names/Trade Names: | |
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Chemical Formula | Arthur Thomas, Gemstones (2009) More from other references |
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Kyanite Treatments |
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Pale blue kyanite (also known as cyanite or disthene) is reported to lose its color on heating to 1200°C (Smith et al, 1978) - Nassau (1984) |
Physical Properties of Kyanite |
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Mohs Hardness | 4 to 7Walter Schumann, Gemstones of the world (2001) More from other references |
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Specific Gravity | 3.55 to 3.70Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Tenacity | BrittleWalter Schumann, Gemstones of the world (2001) |
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Cleavage Quality | PerfectUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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Fracture | SplinteryArthur Thomas, Gemstones (2009) |
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Optical Properties of Kyanite |
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Refractive Index | 1.710 to 1.735Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Optical Character | Biaxial/+,-Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Birefringence | 0.012 to 0.033Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Pleochroism | Blue stones - strong trichroism: colorless/pale blue - (greenish or violet)-blue - dark blueHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Dispersion | 0.020Arthur Thomas, Gemstones (2009) |
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Chatoyancy | RareHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Colour |
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Colour (General) | Blue, blue-green, green, brown, yellow, red, colourlessUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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Causes of Colour | Blue, Fe2+-O-Ti4+ charge transfer, Fe2+-O-Fe3+ charge transfer, Fe2+ and Fe3+ in octahedral coordination can all be involved, with contribution from Cr3+ in octahedral coordination. Green, V3+ in octahedral coordination; Fe3+ in octahedral coordination. Orange, Mn3+. Color change, Cr3+ in octahedral coordinationW. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) |
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Transparency | Transparent,TranslucentWalter Schumann, Gemstones of the world (2001) More from other references |
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Lustre | Vitreous,PearlyArthur Thomas, Gemstones (2009) More from other references |
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Fluorescence & other light emissions |
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Fluorescence (General) | Weak; redWalter Schumann, Gemstones of the world (2001) |
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Fluorescence (Long-Wave UV) | Blue: usually reddishHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Crystallography of Kyanite |
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Crystal System | TriclinicHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Habit | Often fibrousHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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Geological Environment |
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Where found: | Kyanite occurs in gneisses and schists and in granite pegmatites.Michael O’Donoghue, Gems, Sixth Edition (2006) |
Further Information |
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Mineral information: | Kyanite information at mindat.org |
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Significant Gem Localities |
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| Kenya | |
| Natural History Museum Vienna collection | | Madagascar | |
| Madagascar - extraLapis English No.1, p. 92 | | Mozambique | |
| Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 422 | | USA | |
| E.Ya. Kievlenko (2003) Geology of gems, p. 70 |
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