CVD Diamonds with Invisible Markings
Laser inscription is a common practice that helps to easily identify a diamond. The inscriptions are so small as to be nearly impossible to read without magnification, but they can be easily read with a loupe or microscope to help match the diamond to a laboratory report. Laser inscription can be done on the girdle, on the center of the table, on a star facet, or under the table surface. Inscriptions under the table surface are very effective from a security standpoint, as they require significant weight loss to remove.
Recently, GIA labs in India tested two diamonds (1.93 and 0.60 ct) with interesting markings. No intentional markings were observed on these samples without magnification, nor could any be seen under a microscope. But when the diamonds were exposed to the deep ultraviolet light of the DiamondView, markings appeared (see above). Both samples were CVD laboratory-grown diamonds and treated with high pressure and high temperature after growth. The invisible markings are thought to be caused by slightly different concentrations of defects, but we do not know how they were created.
The invisible markings in these two diamonds suggest the possible introduction of a new security measure in diamonds, similar to the anti-counterfeiting measure used with passports and banknotes upon exposure to a special light.
