Topaz is a silicate mineral of aluminium and fluorine.
Topaz has a hardness of 8 by mohs-scale (only Diamond,
Ruby and Sapphire
are harder), the same specific gravity like Diamonds and a vitreous
luster. Natural Topaz mainly occurs in white (colourless), light
blue, yellow, light pink and pale brown - usually in transparent
quality. When heated, yellow Topaz often becomes orange or reddish-pink,
some of the most beautiful colours in the world of gemstones. These
rare and expensive gemstones, called "Imperial-Topaz"
only come from Ouro-Preto (Minas Gerais) in Brazil.
Topaz can be irradiated,
this turns the natural colour to light blue, intense blue or electric
blue. These enhanced colours are usually stable - they are called
sky blue, swiss blue and london blue. Clear Topaz Crystals can reach
sizes of more than hundred pounds, that´s why the price for
Topaz - except the rare colours - is quite low compared to other
gemstones.
Topaz of gemstone-quality is mostly found in Brazil,
Madagascar, Nigeria, Namibia, Russia, Pakistan and Sri Lanka.
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