To evaluate possible problems in separating gem materials coated with a synthetic diamond thin film from their uncoated equivalents, we examined one sample of a free-standing, polycrystalline diamond film about one micron (0.001 mm) thick. This film could be easily recognized by standard microscopic examination, especially in surface-reflected and polarized light. The potential problems related to detecting thicker, monocrystolline, or colored synthetic diamond thin films and coatings that might be encountered in the future on faceted stones are also briefly discussed.
