Zirkon

Zircon: A zirconium-bearing nesosilicate, a member of the garnet group. Its hardness is 7.5; its specific gravity varies remarkably widely from 3.9 to 4.8. It has significant refraction and birefringence, as well as colour dispersion, giving it a bright, diamond-like lustre. Zircon is usually opaque or yellowish brown, reddish brown, grey, greenish or black. Noble zircons, known as gemstones, can also be greenish, rose-red or brownish-yellow.

Found in Sri Lanka, Romania, Austria, Germany, Russia.