Difference between revisions of "GPFDC"
From The Gemology Project
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Revision as of 08:08, 26 July 2007
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Alexandrite | |
---|---|
Chemical composition | Al2(BeO4)Beryllium aluminum oxide |
Crystal system | Orthorhombic |
Habit | Tabular, pseudo-hexagonal |
Cleavage | Imperfect prismatic |
Fracture | Weak, conchoidal |
Hardness | 8.5 |
Optic nature | Biaxial + |
Refractive index | 1.744 - 1.755 |
Birefringence | 0.009 |
Dispersion | Low, 0.014 |
Specific gravity | 3.70 - 3.72 |
Lustre | Bright vitreous |
Pleochroism | Strong |
Alexandrite is a phenomenal variety of the mineral chrysoberyl. Because of trace amount of vanadium and chromium, alexandrite appears different colors depending on whether it is viewed in natural or incandescent light. In daylight, the stone appears to be green; in artificial light it appears to be raspberry red. It was originally discovered in the Ural Mountains in 1830 on the birthday of Czar Alexander of Russia. Another extraordinary coincidence was that the national colors of Russia were red and green. Today, alexandrite is found in Brazil and to a lesser extent in Africa. Alexandrite has long been associated with great luck and prosperity.
Additional Phenomena
- Cat's Eye