Zircon
Zircon is a natural zirconium silicate that comes in every color and has been used as a gemstone for at least 2,000 years. Critically, it is not the same as “cubic zirconia” — a synthetic crystal sold as a cheap diamond simulant. Natural zircon is a legitimate gemstone; cubic zirconia is a lab-grown lookalike.
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Everyday wear comfortably wants a 7+. Below 7, choose settings that protect the stone (bezel, halo) and store the piece carefully.
Zircon’s refractive index (1.93) is close to diamond’s (2.42), which is why pre-modern jewelers used colorless zircon as a diamond substitute long before cubic zirconia existed. It has high dispersion (more rainbow fire than most gems) and excellent brilliance.
Colors and treatments
Most zircon on the market is heat-treated, which is the standard trade practice — heating brown raw material at around 1000°C produces the vivid blue (the most popular variety) and the colorless stones used as accents.
| Treatment | Notes | |
|---|---|---|
| Blue zircon | Heat-treated brown rough | Vivid sky-blue to teal. The most popular zircon color on the modern market. December birthstone. |
| Colorless zircon | Heat-treated | Historical diamond substitute. High refractive index gives genuine sparkle. |
| Natural yellow / orange / red | Untreated | Less common; collectors' market. |
| Natural green | Untreated, slightly radioactive | Trace uranium content. Modern testing confirms safe handling levels, but the variety is niche. |
Daily wear
At Mohs 7.5, zircon is hard enough for daily wear in protected settings. The brittleness — zircon facets chip more easily than tougher stones like sapphire — argues for bezel or partial-halo settings rather than high prongs.
Ultrasonic cleaners are safe on clean stones; warm soapy water for inclusion-bearing stones.
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Written by
Anna
Jeweler · Formi Jewelry
Anna works with Formi clients on stone selection, setting design, and fit — making sure every piece is right before it’s made.
Book a consultation with our in-house jewelersLast updated May 2026