| General Information |
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| A variety or type of: | Chalcedony, which is a variety of Quartz |
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| Chemical Formula | Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Sard Treatments |
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| The color may be lightened by heat-treatment - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 7 |
| Physical Properties of Sard |
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| Mohs Hardness | 6.5 to 7Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Specific Gravity | 2.58 to 2.63Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Cleavage Quality | NoneWalter Schumann, Gemstones of the world (2001) |
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| Fracture | ConchoidalArthur Thomas, Gemstones (2009) |
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| Optical Properties of Sard |
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| Refractive Index | 1.535 to 1.539Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Optical Character | Uniaxial/+Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Birefringence | 0.008 to 0.010Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Pleochroism | AbsentWalter Schumann, Gemstones of the world (2001) |
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| Dispersion | NoneWalter Schumann, Gemstones of the world (2001) |
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| Colour |
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| Colour (General) | BrownUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references |
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| Transparency | Translucent,OpaqueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Lustre | Waxy,ResinousArthur Thomas, Gemstones (2009) |
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| Crystallography of Sard |
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| Crystal System | TrigonalUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Habit | Fibrous to grained aggregateUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Further Information |
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| Mineral information: | Sard information at mindat.org |
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