Скачать или смотреть The Surprising History of Topaz: A Gem of Royalty

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General Topaz Information Via Mindat:
Formula: Al2(SiO4)(F,OH)2
Colour: Colourless, white, pale blue, light green, yellow, yellowish brown, or red
Lustre: Vitreous
Hardness: 8
Specific Gravity: 3.4 - 3.6
Crystal System: Orthorhombic
Name: Named after Topazios Island (currently called Zabargad Island or St. John's Island) in the Red Sea. In antique times, the name was probably used for the gemstone that is now known as peridot.
Occurs in pegmatites and high-temperature quartz veins, also in cavities in granites and rhyolites.

A maximum of ~30 % of the F site is occupied by OH in natural topaz, although in some very rare cases OH-dominant members have been described in high-pressure rocks, see Unnamed (OH-analogue of Topaz) (Zhang et al., 2002). A pure synthetic OH analogue of topaz has been synthesised under conditions of high pressures (between 55 and 100 kbar) and high temperatures (up to 1000 °C) (Wunder et al., 1993).
Note that topaz is either orthorhombic or triclinic, depending on the F:OH ratio.

Topaz is one of the most interesting minerals on the market today, and quite affordable overall with the discovery of large trends in Brazil. In this History of Birthstones video I'll be discussing some interesting tidbits about the November Birthstone, Topaz. Where is it found? What is the interesting history or lore behind it?

#topaz #crystals #gems #nature #minerals #mineralogy #history