Difference between revisions of "Topaz"
From The Gemology Project
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==Synthetics== | ==Synthetics== | ||
− | Although topaz is | + | Although topaz is synthesized, the material is not commercially available. |
==Sources== | ==Sources== | ||
* [http://www.gia.edu/newsroom/issue/2798/2696/insider_newsletter_details.cfm#2 From Gems & Gemology: A New Imitation of Imperial Topaz] | * [http://www.gia.edu/newsroom/issue/2798/2696/insider_newsletter_details.cfm#2 From Gems & Gemology: A New Imitation of Imperial Topaz] |
Revision as of 05:02, 30 June 2007
Topaz | |
---|---|
Chemical composition | Al2(F,OH)2SiO4 |
Crystal system | Orthorhombic |
Habit | Prismatic with pyramidal/domed terminations |
Cleavage | Perfect, basal plane |
Fracture | Sub-conchoidal to uneven |
Hardness | 8 |
Optic nature | Biaxial + |
Refractive index | 1.606-1.644 |
Birefringence | 0.008 - 0.010 |
Dispersion | Low, 0.014 |
Specific gravity | 3.49 - 3.57 |
Lustre | Vitreous |
Pleochroism | Distinct to strong (depending on body color) |
Imitations
Recently,2007, yellow-orange-pink flame-fusion corundum is offered in Minas Gerais, Brazil as imperial topaz.
Synthetics
Although topaz is synthesized, the material is not commercially available.