A to Z of Gemstones: T: Topaz


Gemstone family: Topaz

Crystal System: Orthorhombic

Moh's scale of hardness: 8

Lustre: Vitreous

Birthstone: November

About: Topaz can occur in a wide range of colours; from light to deep blue, golden yellow, orange, brown, bright pink, red, purple, green or colourless. The different colours are caused by colour-centres or traces of the mineral chromium. Blue Topaz has 3 different shades: Sky Blue (a very pale blue), Swiss Blue (a very vivid turquoise blue, almost electric) and London Blue (a dark teal blue) Usually, Topaz has very few inclusions and looks clean to the naked eye.

Origin: Brazil is one of the main sources of Topaz, it can also be found in Russia, Sri Lanka, Afghanistan and the USA.

Use in jewellery: Topaz's hardness makes it suitable for all types of jewellery.

Treatments, synthetics and imitations:  Much blue topaz encountered today has resulted from irradiation and heating of natural colourless topaz.  Pink topaz can also be heated.  Green diffusion treated topaz is also widely available.  Mystic topaz is colourless topaz which has been artificially coated via a vapour deposition process giving it a rainbow effect on its surface.