The zircon is a natural gemstone not so well-known and often confused with cubic zirconium (synthetic material create to imitate diamond with different chemical composition).
It is colorless when it's pure, these are inclusions who give it colors : blue, red, brown, yellow, orange and rarely green.
The zircon is a new way to ride up time. In fact, zircon is one of the oldest material on Earth. The oldest specimens comes from Jack Hills in Australia.
Heated between 800° and 1000°C, the brown zircon can become bleu and the light blue can become bright blue.
To know more about mineralogy of the zircon see mindat.org->