Zircon is a zirconium silicate that crystallizes in the tetragonal crystal system. It is highly dispersive and brilliant. Natural zircons range from colorless to pale yellow or green. These colors result from trace amounts of hafnium, uranium and thorium. Over time, these radioactive components break down the lattice of the crystal, eventually (over tens of thousands of years) destroying the crystal, leaving it with an amorphous structure and a dark pithy appearance.

Zircons that are young and unaffected by radioactivity are termed high zircons. These stones are transparent yellowish-green, golden and greenish-brown in color with extremely high dispersion. High zircons can be heated and become colorless or blue. These heat-treated zircons imitate diamond's optic properties better than any other naturally occurring gem mineral. For that reason, they have long been used as diamond substitutes. That is why the name zircon has been associated with being synthetic or imitation.

Zircon is a relatively common constituent of igneous rocks, particularly granite. Inclusions of zircon, containing Uranium 235 have been geologically used to positively date rock formations. Gemstone crystals are quite rare and usually occur in coarse-grained pegmatites. They are also found accumulated in alluvial deposits because of their high specific gravity.