Almost every buyer encounters the words “heated” or “treated.” Understanding what they mean removes a great deal of confusion — and risk.
What “treatment” means
Treatment is any process, beyond cutting and polishing, used to improve a gem’s appearance or durability. Treatments range from long-accepted (heat) to those that significantly affect value and require careful disclosure.
Heat treatment of sapphire
Heating is an ancient, stable and widely accepted treatment that improves a sapphire’s colour and clarity. The result is permanent and does not make the stone any less “natural” in material — but it does affect value relative to an unheated equivalent.
Untreated stones and premiums
Unheated sapphires of fine colour are scarcer and command a premium, particularly in larger sizes. For some buyers — including many seeking sapphires for astrological use — untreated status is essential.
Disclosure is everything
The key principle is honesty: a reputable seller discloses treatment in writing on every stone, and significant purchases should be backed by an independent report confirming the status.
