Archive for the Organic Gemstones Category
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Refractive Index : 1.550 – 0.010
Optical Characteristic : SR
Specific Gravity : SG 1.29 + 0.06 – 0.03
Formula : organic protein material
Crystal System : Organic
Variety/Species : All
Species/Group : Tortoise shell
Birefringence : None
Dispersion : None
Hardness : 2.5
Toughness : Fair
Ultrasonic : Never
Steam : Never
UV Long : Inert to moderate
UV Short : Inert to moderate
Pleochroism : None
Strength : N/A
Pleochroism [...]
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Refractive Index : 1.685-1.530
Optical Characteristic : AGG
Specific Gravity : 2.89-2.81
Formula : Mostly CaCO3
Crystal System : Organic
Variety/Species : Tridacna Pearls
Species/Group : Calcareous concretons
Birefringence : 0.155
Dispersion : N/A
Hardness : 2.5 to 4
Toughness : Fair to poor
Ultrasonic : Never
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : None
Strength : N/A
Pleochroism Colors : None
Heat : sensitive
Acids : sensitive
Light [...]
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Refractive Index : 1.540 – 1.535 spot 1.540
Optical Characteristic : AGG
Specific Gravity : 2.00 – 1.70
Formula : Calcium phosphate, collagen and elastin.
Crystal System : Organic
Variety/Species : Ivory
Species/Group : Ivory
Birefringence : none
Dispersion : none
Hardness : 2.25 to 2.75
Toughness : fair
Ultrasonic : Never
Steam : Never
UV Long : weak to strong bluish white or violet blue
UV Short : [...]
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Refractive Index : 1.680 – 1.520
Optical Characteristic : AGG
Specific Gravity : 2.85 – 2.60 (usually about 2.70)-varies with mineral content
Chemical composition : Often Variable, usually aragonite, calcite, pyrite, silica and more
Crystal System : Organic
Variety/Species : None
Species/Group : Ammonite
Birefringence : 0.155 (varies)
Dispersion : None
Hardness : 4.5 to 5.5
Toughness : Fair to poor
Ultrasonic : Never
Steam : Never
UV Long [...]