Topaz

The name topaz is thought to derive from the Sanskrit word tapas meaning fire, and when you encounter a precious topaz stone first hand there is no doubt in regards to why it was given that name.

True precious topaz is rarely seen in jewellery despite being a beautiful and versatile gemstone. It comes in a range of gentle colours depending on the impurities present. The most common natural colours are yellow, yellow-brownish, orange-brownish, a pinky brown, light to medium red, blue and colourless. More rarely, topaz can be found in light green, pink, pink-red, light greenish yellow and violet. The most expensive and desirable colours are the sherry topaz (a reddish orange colour that is occasionally confused with citrine), precious imperial topaz (a fine apricot-range colour) and pink topaz (which can vary from pale pink to violet-pink).

Much colourless topaz is irradiated and heat-treated to a range of blues, some to the point where they are almost indistinguishable from aquamarine when seen with the naked eye. Some topaz has tear-shaped cavities, containing a gas bubble or several immiscible (non-mixing) liquids. Other inclusions such as cracks, streaks and veils also occur. Topaz is a durable stone with a reasonable hardness and is impervious to most scratching.

As the colour of topaz is rarely vivid, cuts such as step cuts or scissor cuts are used to display it at its best. Topaz has a high brilliance and vitreous lustre, so colourless or weakly coloured material is often faceted as a brilliant cut in order to provide a lively gemstone that is a cheaper alternative to corundum or diamond.

Sources:
Judith Crowe, The Jeweller's Directory of Gemstones (London: A&C Black, 2006)
Cally Hall, Gemstones (London: Dorling Kindersley, 1994)
Jaroslaw Bauer and Vladimir Bouska, A Guide in Colour to Precious & Semiprecious Stones (London: Octopus Books, 1983)