Shell Pearl as a Pearl Imitation
Examination of commercially-available "shell pearls" reveals imitation material.
Fancy Black NPD Synthetic Diamond
Testing reveals the first synthetic nano-polycrystalline diamond (NPD) to be detected by a gem lab.
Spring 1991 G&G Lab Notes
This section, from the Spring 1991 issue of Gems & Gemmology, is a compilation of interesting finds from GIA’s laboratories.