http://www.all-gemstones.com www.all-gemstones.com    Thu, 06 May 2010 12:29:47 +0000 http://wordpress.org/?v=2.8.6 en hourly 1 http://www.all-gemstones.com/alexandrite http://www.all-gemstones.com/alexandrite#comments Wed, 29 Jul 2009 14:09:08 +0000 admin http://www.all-gemstones.com/?p=374 Natural Alexandrite Gemstone Refractive Index : 1.755 – 1.746 (+0.004 – 0.006) Optical Characteristic : DR, biaxial positive Specific Gravity : 3.73 (+0.02 – 0.02) Formula : BeAl2O4 Crystal System : Orthorhombic Variety/Species : Natural Alexandrite Species/Group : Chrysoberyl Birefringence : 0.008 – 0 .010 Dispersion : 0.015 Hardness : 8.5 Toughness : Excellent Ultrasonic : Usually Safe Steam : Usually Safe UV Long : Inert to moderate red UV Short : Inert to moderate red Pleochroism : 3 Colors Strength : Strong

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Pleochroism Colors : Strong, green, orange and purple red Heat : Stable Acids : No reaction Light : Stable Polish Luster : Vitreous to subadamantine Fracture : Conchoidal Fracture Luster : Vitreous to greasy Clarity Type : II Tones : 2-8 Saturations : 1-3 Cause of Color : Chromium Enhancements : None Cleavage : None. Color Range : Daylight: strongly bluish green, green, yellowish greenIncandescent: orangy red, red, purple-red, purplish red, red-purple Purplish, reddish, bluish, greenish Transparency : Transparent Phenomena : Asterism, color change, 4 ray star chatoyancy

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Separations : Alexandrite from-Andalusite : RI, SG, pleochroism, spectrumColor change garnet: RI (pos) birefringence, optic character, pleochroism, spectrum, magnification.All corundum: RI, optic character, spectrum, magnification, SG.All spinel: RI, birefringence, optic character, magnification, SG.Synthetic Alexandrite: magnification, fluorescence (possibly) Identifying Characteristics and informationUsually biaxial positive (DR B+) but may be biaxial negative (DR B-).Color change.Fingerprint inclusion, silk, include crystals, and liquid inclusions.May fluoresce a weak red (LW and SW) Spectral DataNarrow doublet@ 6805 6975. Weak, narrow lines@ 6650, 6650, 6490 and broad band @ 6400-5550. Trade Names and Misnomers
Alexandrite
Cat’s Eye alexandrite (S) ]]> http://www.all-gemstones.com/alexandrite/feed 0