A color treatment is any process that changes a diamond's color, such as HPHT processing or coating.
In more detail
A stable color treatment such as HPHT is graded and disclosed. Coating is unstable, so GIA doesn't grade a coated diamond.
On a grading report
GIA adds an asterisk after the color grade and explains the treatment in Comments. It inscribes TREATED COLOR on an HPHT-treated stone.
Related terms
- Asterisk after the color grade: An asterisk (*) after a GIA color grade means that the lab detected a color treatment. Comments explains what it is.
- HPHT: HPHT stands for high pressure, high temperature. The same conditions can grow a diamond in a laboratory or treat a natural one to change its color.
- Coating: Coating is a thin film, paint or ink on the surface of a gem that changes its color or look.
- Treatment: 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.