USA
2.63 carats
© Palagems
General Information | |||||||||||
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Chemical Formula |
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Significant stones | |||||||||||
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Benitoite Treatments | |||||||||||
The deep blue color observed in some benitoite may have the same iron-titanium charge-transfer origin as does the blue in sapphire. It is doubtful that any of the corundum heat treatments could be applied successfully, however, since benitoite has a much lower melting point, being a silicate of composition BaTiSi3O9. G. Rossman has found (unpublished data) that benitoite gradually loses its blue color on heating in air at 600°C for 19 h. Irradiation with cobalt 60 returned some of the color center that is unrelated to the natural color – Nassau (1984) Heat-treatment may produce pinkish orange colors - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p. 3 Only the rare colourless benitoite can be heat-treated and will change to peachy/orange colour. Blue benitoite cannot be heat-treated. - Personal communication, 2014. | |||||||||||
Physical Properties of Benitoite | |||||||||||
Mohs Hardness | 6 to 6.5Blue Chart Gem Identification (2010) , More from other references | ||||||||||
Specific Gravity | 3.61 to 3.68Blue Chart Gem Identification (2010) , More from other references | ||||||||||
Tenacity | BrittleGemstones of the world (2001) , | ||||||||||
Cleavage Quality | IndistinctGemstones of the world (2001) , More from other references | ||||||||||
Fracture | ConchoidalGemstones (2009) , | ||||||||||
Refractive Index | 1.757 to 1.804Blue Chart Gem Identification (2010) , More from other references | ||||||||||
Optical Character | Uniaxial/+Blue Chart Gem Identification (2010) , More from other references | ||||||||||
Birefringence | 0.047Blue Chart Gem Identification (2010) , DoublingMore from other references | ||||||||||
Pleochroism | Strong dichroism: blue - colorlessBlue Chart Gem Identification (2010) , More from other references | ||||||||||
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