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The Pennyweight

Glossary · Fine Jewelry

Treated Stone

A treated stone has been altered after cutting to change its appearance: clarity enhancement fills fractures, irradiation and HPHT shift colour, and heat improves the great majority of sapphires and rubies. Treatment is legal and common, and much of it is stable — but it must be disclosed, and it changes both value and care instructions. Fracture-filled stones in particular can be damaged by ordinary repair heat.

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