A treatment is any process, other than cutting and polishing, that changes a gem's color or apparent clarity. Anyone who sells a treated gem must disclose the treatment.
In more detail
Common treatments in colored stones are heating, diffusion, filling, irradiation, dyeing and coating. Some are stable and permanent; others need special care. For diamonds, GIA grades permanent treatments, such as HPHT color treatment and laser drilling. Unstable ones, such as coating and fracture filling, get only an Identification Report.
On a grading report
Labs list detected treatments under Comments or Further information. On a GIA diamond report, a color treatment also adds an asterisk to the color grade.
Related terms
- Heat treatment: Heat treatment is controlled heating of a gem to change its color or clarity.
- Beryllium diffusion: Beryllium diffusion is heating corundum with an added element, such as beryllium. The element diffuses into the crystal and changes its color.
- Clarity enhancement: Clarity enhancement is filling surface-reaching fissures with a filler such as oil, resin, wax or glass, so they show less.
- Color treatment: A color treatment is any process that changes a diamond's color, such as HPHT processing or coating.
- Laser drilling: Laser drilling is a clarity treatment that bores a tiny channel to an inclusion, usually a dark one. The laser then burns the inclusion away, or a bleaching agent enters through the channel.
- Disclosure: Disclosure is telling the buyer, before the sale, that a gem is treated, laboratory-grown or an imitation.