Archive for the Tourmaline Category
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Refractive Index : 1.786 – 1.729
Optical Characteristic : DR, uniaxial negative
Specific Gravity : 3.32
Formula : NaMg3V6(Si6O18)(BO3)3(OH)4
Crystal System : Trigonal
Variety/Species : Tourmaline
Species/Group : Tourmaline Group
Birefringence : 0.057
Dispersion : 0.017
Hardness : 7.5
Toughness : Fair
Ultrasonic : Risky
Steam : Risky
UV Long : Inert
UV Short : Inert
Pleochroism : 2 colors
Strength : Moderate to strong
Pleochroism Colors : No data
Heat : May [...]
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Refractive Index : 1.654 – 1.635
Optical Characteristic : DR, Uniaxial negative
Specific Gravity : 3.01
Formula : NaAI3AI6(BO3)3(Si6O18)(O,OH)4
Crystal System : Trigonal
Variety/Species : Tourmaline
Species/Group : Tourmaline
Birefringence : 0.019
Dispersion : 0.017
Hardness : 7 to 7.5
Toughness : Fair
Ultrasonic : risky
Steam : risky
UV Long : Inert
UV Short : Inert
Pleochroism : 2 colors
Strength : moderate to strong
Pleochroism Colors : pinkish yellow/ bright [...]