Zircon is an important gemstone of many colors, and is an historical gemstone used for thousands of years. It is sometimes looked upon as a cheap Diamond simulant, but in actuality it can be a valuable gem. Its color diversity is caused by traces of certain impurities, some of which are radioactive. Zircon gemstones containing radioactive element traces undergo a process called metamiction, in which their inner crystal structure becomes destroyed. These radioactive forms of Zircon must be heated to stabilize them for use as gems.