What is Zircon?
Zircon is a dense and durable zirconium silicate, loved as a gemstone and valued by geologists as one of the most reliable natural clocks for dating rocks.
Mineralogy and structure
Reference formula: ZrSiO4. Zircon is tetragonal with the ideal formula ZrSiO4. Its high density, resistance to weathering and trace uranium make it a key geochronology mineral. Some old grains become metamict through radiation damage, so colour and clarity must be interpreted with the structure and analysis. Zircon is classified with silicates and has tetragonal crystal symmetry. Typical hardness is 7.5–7.5 on the Mohs scale and specific gravity is approximately 4.6–4.8.
Colour, lustre and habit
Typical colours include brown, colourless, yellow, red, green, blue. The usual prismatic, tabular, granular habit and adamantine, vitreous, resinous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Zircon forms in or is associated with igneous crystallisation, metamorphic recrystallisation and sedimentary placer concentration. Important documented localities include Sri Lanka, Cambodia, Myanmar, Madagascar, Australia, Norway, Canada and Pakistan.
A gemstone with a geological memory
A fine zircon brings together colour, brilliance and deep time. Clear blue, golden or red crystals are highly desirable in jewellery, while inclusion-rich grains are prized as miniature records of Earth's history.
Collecting and care
Protect faceted stones from hard knocks despite their high hardness. Do not heat, irradiate or acid-test an inclusion-rich specimen without professional control; retain locality and treatment information.
