GIA Identifies an Atypical Saltwater Pearl

The Gemological Institute of America (GIA) recently examined an undrilled white semi-baroque nacreous saltwater pearl.

The institute received the 8.98-carat bead at its laboratory in Mumbai. The pearl displayed dents and wrinkles on the surround, like those seen in cultured pearls, according to an article in the winter issue of the GIA’s quarterly journal, Gems & Gemology. 

X-ray imaging showed a dense internal structure that was missing the growth features typically present in natural or cultured pearls of this size. To examine the pearl further, the lab undertook CT imaging, which revealed a subtle outline, a feature consistent with a potential bead nucleus. Overall, this suggests the pearl was probably bead cultured, although its internal structure is unusual.

Bead-cultured pearls are usually easy to identify because they show a distinct dark grey outline of the round bead nucleus used in cultivation, sometimes with small organic gaps. In this case, the pearl had a more blended, uniformly opaque structure, with the bead nucleus appearing more radiopaque than a conventional freshwater shell bead.

The pearl was non-reactive under X-ray fluorescence (XRF) confirming a saltwater origin and suggesting the bead was made from a non-standard material.

It was difficult to identify the material used for the bead nucleus conclusively because the pearl showed no fluorescence or shell banding, and only slight variations in radiopacity between the bead nucleus and the outer nacre area.

New pearl-culturing methods and materials have made some specimens harder to distinguish. In some cases, relying only on X-ray imaging can result in misidentification. Using CT scanning has proven essential for accurately identifying these challenging pearls, GIA stated.

Image: The 9-carat saltwater pearl. (Gemological Institute of America)