The Probert Encyclopaedia of Rocks & Minerals

ZIRCON

Zircon (zirconium silicate) has the formulae ZrSiO4 and a relative hardness of 8. It is a common accessory mineral found in all types of igneous rocks. When transparent it's used as a gemstone.
Zircons contain abundant radioactive isotopes of uranium and so are useful for uranium-lead dating to determine the ages of rocks.
Research Zircon