A to Z of Gemstones: Z: Zircon


Crystal System: Tetragonal

Moh's scale of hardness: 6.5-7.5

Lustre: Vitreous to sub-adamantine

Birthstone: December

About: Zircon  can be blue, colourless, red, yellow, orange, brown and green. It has a bright lustre and high dispersion.

Origin: The main sources of zircons are: Sri Lanka, Myanmar, Vietnam, Cambodia, Australia and Madagascar.  

Use in jewellery: Zircon is very brittle, so the facet edges can easily chip and abrade.  For this reason Zircons are better suited to earrings and pendants, where the stone will not get knocked.

Treatments, synthetics and imitations:  Many of the sky blue, colourless and golden are heat treated.  Colourless Zircon is often used to simulate Diamond, but can be distinguished by the doubling of the back faceted, visible with a 10x loupe.