Zircon

Characteristics

• Habit - prismatic to dipyramidal
• Form - tetragonal
• Hardness - 4.6 - 4/7
• Cleavage - imperfect
• Fracture - uneven to conchoidal
• Streak - white
• Lustre - adamantine to oily
• Colour - colourless, yellow, grey, green, brown, blue, red

Introduction

One of the few stones to approach diamond in fire an brilliance - has high refractive index and dispersion; has been used in the past to imitate diamonds; Don't confuse with Cubic Zirconia (CZ) which is synthetic with a different chemical composition and atomic structure.

At end 19th century most known were green or reddish-brown but today many are bright blue due to heat treatment of the brown zircon.

Found in metamorphic rocks and silica rich igneous rocks. Resists weathering. Is found in stream and river gravels and beach deposits; Can have large crystals eg: weighing up to 2kg in Australia and 4kg in Russia.

Susceptible to brittle fractures and facet edges are easily damaged so don't let stone rub together and wear with care. Avoid heat and bright sunlight as the colour can change.

In identification can see a 'doubling' of the back facets as you look through the stone.

Lore: Takes name from Arabic zargun, in turn from Persian zar (meaning gold) and gun (meaning colour); Dec birthstone