Gemstones
Topaz: From Sherry Brown to Swiss Blue
Most blue topaz on the market is colourless topaz that has been irradiated and heated, a disclosed and stable treatment distinct from natural imperial topaz.
Natural colour range
Topaz occurs naturally in colourless, light blue, and prized orange-pink 'imperial' tones. Natural, untreated blue topaz is rare compared with the vivid blue commonly seen in jewelry stores.
Irradiation and heat treatment
Most Swiss and London blue topaz is produced by irradiating colourless topaz and then heating it to stabilise the colour. The result is permanent and safe, but should be understood as a treated, not natural-colour, stone.
Imperial topaz
Imperial topaz, with its warm orange-pink hue, is typically untreated and significantly rarer and more valuable than treated blue varieties.
Buyer checklist
- ✓ Assume common blue topaz is irradiated and heat-treated
- ✓ Ask for documentation on imperial topaz given its rarity
- ✓ Check hardness suitability (8 Mohs, but can cleave if struck)
Verification tools & references
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