Zircon

Zircon is most famous for its colourless stones which closely resemble diamonds, and therefore have been used both intentionally and mistakenly in their place. Although colourless when pure, impurities can produce yellow, orange, blue, red, brown and green varieties. The most common are grey-brown to red-brown, while the most popular is golden brown. Pure, colourless zircon is rarer but worth the search due to its brilliance and fire.

It’s difficult to understand why zircon isn’t more popular considering it contains a hardness comparable with garnets and tourmalines, it features an adamantine lustre identical to diamonds, it has a strong double refraction in addition to its wide variety of attractive colours and its affordability.

However, despite its applicability the zircon stone it is often confused with cubic zirconia, a synthetic stone purposefully grown as a substitute for the diamond. Whether the mix-up is due to the similarity in names or simply a lack of awareness we will never know, but the quality between the two is beyond comparison.

The most surprising fact about the zircon nonetheless is the presence of radioactive materials such as thorium and uranium in certain varieties. The radioactive traces are minute and in no way harmful, but as it slowly deteriorates it also breaks down the crystal structure of the stone which was lead to the distinction between low and high zircon depending on whether it’s damaged or not.

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)