| General Information |
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| Chemical Formula | Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Physical Properties of Grandidierite |
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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 | 2.85 to 3.00Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Cleavage Quality | DistinctUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Fracture | UnevenArthur Thomas, Gemstones (2009) |
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| Optical Properties of Grandidierite |
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| Refractive Index | 1.578 to 1.639Herve 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 | 0.037 to 0.039Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Pleochroism | Distinct: greenish blue - colorless - blue-greenHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Colour |
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| Colour (General) | Bluish-green, blueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Transparency | TranslucentUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Lustre | VitreousArthur Thomas, Gemstones (2009) |
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| Fluorescence & other light emissions |
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| Fluorescence (General) | InertHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Crystallography of Grandidierite |
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| Crystal System | OrthorhombicHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references |
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| Habit | Elongated anhedral crystalsMichael O’Donoghue, Gems, Sixth Edition (2006) More from other references |
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| Geological Environment |
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| Where found: | Grandidierite occurs in aluminous boron-rich rocks and in pegmatites.Michael O’Donoghue, Gems, Sixth Edition (2006) |
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| Inclusions in Grandidierite |
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| Needle-like channels, parallel growth planes - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 6 |
| Further Information |
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| Mineral information: | Grandidierite information at mindat.org |
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| Significant Gem Localities |
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| Madagascar | |
- Taolañaro (Fort Dauphin)
| Gems, Sixth Edition, Michael O’Donoghue, 2006, p.414 |
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