Topaz: Nesosilicate mineral
Topaz is a silicate mineral.
Along with silicate, it includes the chemical elements aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2.
| Topaz | |
|---|---|
 Topaz crystal on matrix | |
| General | |
| Category | Nesosilicate |
| Formula (repeating unit) | Al2SiO4(F,OH)2 |
| Strunz classification | 9.AF.35 |
| Crystal symmetry | Orthorhombic dipyramidal H-M symbol: (2/m 2/m 2/m) Space group: Pbnm |
| Unit cell | a = 4.65 Å, b = 8.8 Å, c = 8.4 Å; Z = 4 |
| Identification | |
| Color | Colorless (if no impurities), blue, brown, orange, gray, yellow, green, pink and reddish pink |
| Mohs scale hardness | 8 (defining mineral) |
| Luster | Vitreous |
| Birefringence | δ = 0.010 |
| References | |
Color and varieties
Pure topaz is colorless and transparent but they usually have colors made by small impurities. The typical topaz is wine, yellow, pale gray, reddish-orange, or blue brown. It can also be made white, pale green, blue, gold, or pink (rare).
Orange topaz, also known as precious topaz, is the traditional November birthstone, the symbol of friendship, and the state gemstone for the US state of Utah.
Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Some imperial topaz stones can fade if they are exposed too much in the sunlight.
Blue topaz is the US state Texas' gemstone.
Mystic topaz is colorless topaz which has been artificially coated, making it rainbow-colored.
Gallery
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Colorless topaz, Minas Gerais, Brazil -
A cut blue topaz -
A red topaz -
Imperial Topaz Gem -
Facet Cut Topaz Gemstones in various colors, including mystic.
Related pages
References
Other websites
- Pink Topaz, Biblical Topaz References Archived 2009-08-15 at the Wayback Machine Farlang – gem information and full text historical references
- Topaz and other minerals found at Topaz Mountain, Juab County Archived 2013-08-27 at the Wayback Machine, Utah Geological Survey
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