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.
