gems, diamond, coated diamond

Gemmologists who grade diamonds should be aware of unusual features that I noted recently while examining four diamonds. The four stones, set into two different rings, were in the estate of an elderly woman who had worn the rings constantly for over fifty years while she lived in Deland, Florida. One diamond of 1.82 ct was set as a solitaire, and the other three stones, 1.23 ct, 1.53 ct, and 1.25 ct (all weights estimated by Leveridge method), were set side-by-side into the second ring. The first unusual feature of these stones was that they all fluoresced a brownish-yellow under short-wave ultraviolet light. The large solitaire showed a strong brownish-yellow fluorescence, while in the second ring the stones showed approximately the same brownish-yellow fluorescence although less intense. Another unusual feature of the stones was that they showed evidence of a coating even though they had been thoroughly cleaned in a professional ultrasonic unit. At first I supposed that the coating had been nefariously applied, but then realized that it was too haphazardly placed for that to be the case and was most probably accidental. The coating looked like water spotting that had dried in a somewhat scalloped design around many of the facet junctions. Additionally, the coating in all cases covered the table completely.