White topaz (or colourless topaz) is formed by fluorine-bearing vapours given off during the last stages of the crystallization of"igneous rocks. In its purest form topaz is in fact colourless, it is irradiated then heat treated to give it the different tones it is famous for today. Pure topaz may be colourless and, when brilliant cut has been mistaken for diamond. The"name topaz comes"from Topazios, the old Greek"name"for a small island in the Red Sea, now called Zabargad. It once was a source of peridot which was confused with topaz before the development of modern mineralogy. Mohs Scale of mineral hardness: 8