Feature Gems & Gemology, Spring 1997, Vol. 33, No. 1

Gemological Properties of Near-Colorless Synthetic Diamonds

Examination of 51 colorless to near-colorless synthetic diamonds from all known sources of production confirms that they can be distinguished from similar-appearing natural diamonds on the basis of their gemological properties. Although some may contain opaque metallic inclusions, the most distinctive feature of near-colorless synthetic diamonds is their luminescence to ultraviolet radiation and to an electron beam (cathodoluminescence). In particular, almost all fluoresce yellow or yellow-green to short-wave UV and, when the ultraviolet lamp is turned off, they continue to phosphoresce for 60 seconds or more. These distinctive reactions to ultraviolet radiation are very useful in identification, because many diamonds can be checked at one time.