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Rough Topaz is mostly associated with blue these days; it actually comes in a wide range of attractive colors, with the sunset orange variety, Imperial Topaz, the most valuable.
Rough Topaz has been used to refer to yellowish gemstones for at least two thousand years, although early rough gemstone traders did not realize that these yellow gemstones could be a variety of different crystals. As rough gemstone traders began to get more sophisticated, they realized that these yellow gemstones may be sapphire, quartz, beryl, or what we now know as topaz.
The name topaz may have been derived from the Greek island of Topázos in the Red Sea where a yellow gemstone was mined and the Greek verb topazein meaning ‘to try to find’ but we prefer the Sanskrit word ‘Tapas’ meaning heat or fire as the source of the modern ‘topaz’ as it more captures the brilliance of the gemstone. Rough Topaz makes an ideal gemstone. It comes in a wide range of colors. Its relatively hard qualities allow for many uses.
Gemological Properties of Rough Topaz:
| Chemical Formula | Al2 SiO4 (F, OH) 2 Fluor containing aluminum silicate. |
| Crystal Structure | Prisms with multi-faceted ends, orthorhombic, often octagonal in cross-section. |
| Color | Colorless, light to dark blue, yellow, orange, red-brown, pink-red, red, violet, light green. |
| Hardness | 8 on the Mohs scale |
| Refractive Index | 1.609 – 1.643 |
| Density | 3.49 – 3.57 |
| Cleavage | Perfect |
| Transparency | Translucent to transparent |
| Double Refraction or Birefringence | 0.008 to 0.016 |
| Luster | Vitreous |
| Fluorescence | Under long wavelength UV, white and blue shows a weak yellow or greenish glow; yellow, brown, and pink can show a robust orange-yellow glow; red shows a soft yellow-brown glow. |
Check out our Rough Topaz category for large pieces of rough that are ideal to practice faceting on. The Loose Topaz and Topaz Specimens category has some beautiful terminated examples of various colors of Topaz.
