| General Information |
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| Chemical Formula | Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Coral Treatments |
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| Dyed: mostly with polymer treatment, color and resin concentration in fractures, cavities and branches junctions. Hot point test (acetone test in some cases) may reveal the treatment. Dyed pink to red from white variety: color dignostic if from "bamboo" type (natural color is white to brownish). Dyed blue from grayish: commonly with resin treatment: light blue color concentration in pits and cracks - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 9 |
| Coral Simulants |
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| Artificial pressed product (ceramics) consisting of calcite - Red; opaque; RI 1.486 - 1.658; Birefringence 0.172; Uniaxial/-; SG 2.60 - 2.70; Hardness 3.5 - 4; Trigonal. - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 3 |
| Physical Properties of Coral |
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| Mohs Hardness | 3.5 to 4Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Specific Gravity | 2.60 to 2.70Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Optical Properties of Coral |
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| Refractive Index | 1.486 to 1.658Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Optical Character | Uniaxial/-Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Birefringence | 0.172Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Colour |
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| Colour (General) | Red, pink, white, orange, blue, brownUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Transparency | OpaqueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Fluorescence & other light emissions |
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| Fluorescence (General) | Dull purplish-redHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Crystallography of Coral |
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| Crystal System | TrigonalUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) |
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| Habit | Distinctive wavy parallel fibrous structureHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) |
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| Further Information |
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| Mineral information: | Coral information at mindat.org |
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