Topaz is a fascinating gemstone, and measures eight on the Mohs scale of hardness it’s a popular choice for jewellery, but do you know what colour topaz is or even how those colours can be created?
Natural topaz comes in a wide spectrum of colours with shades from colourless to yellow, orange, to brown, pink to red and blue too. Some natural shades of topaz are rare and can fetch a premium price, such as sherry (deep golden brown), imperial (apricot coloured), or pink topaz.
However, some topaz has been manipulated by certain treatments to alter its colour. These are known as irradiation, diffusion and heat treatments.
Irradiation is a process where gemstones are exposed to radiation. It can intensify orange and yellow shades and even change colourless topaz to blue, such as the fantastic London blue topaz with its dark greyish blue hues. After the treatment, the topaz can remain radioactive for a period of time depending on the quality of the stones and it needs time to “cool” before being suitable to trade. Additionally, strict regulations are in place that protects gem cutters, dealers and consumers alike, so you can enjoy your jewels with no worries! Diffusion treatments create green to blue-green topaz. It involves heating the topaz for a long period of time with a chemical contact that alters the surface colour of the stone but doesn’t change the stone's core colour, effectively only a surface treatment for the stone. Heat treatment is a common process for gemstones, the treatment involves heating and cooling a stone for specific time periods to create the desired colour effect. In the case of topaz, heat treatment can change a brown stone to a more desirable pink colour.
All of these processes produce stunning colour ranges in topaz at an affordable price, perfect if you are on a budget but want a stunning coloured gemstone in a special piece of jewellery.