26. Zircon
A gemstone that is looked upon as a diamond simulant, zircon has been around for thousands of years and is a valuable gem in its own right. The availability of the gem in a multitude of colours is caused by traces of certain impurities found in the mineral, some of which are radioactive. Prior to being used in jewellery, zircons are required to undergo a procedure known as metamiction, which destroys the radioactive traces within the stone. Zircons are usually heat treated to increase their colour and transparency. In nature, they occur in clear, orange, brown, yellow and red.
