Non-Bead-Cultured Pearls from Pinctada margaritifera

Pinctada margaritifera (black-lipped pearl oyster) shells together
Gray to black cultured pearls from the Pinctada margaritifera mollusk, commonly referred to as "Tahitian pearls," are in great demand globally. These often have striking overtones or secondary hues such as green, pink, purple, or a combination of colors. The majority of commercially produced Tahitian pearls are from French Polynesia. They are typically bead cultured, but some non-bead-cultured (NBC) pearls also occur as a by-product and are very marketable in their own right.

A new report from GIA's Bangkok laboratory, "Non-Bead-Cultured Pearls from Pinctada margaritifera," examines a set of 120 NBC samples stated to be of Tahitian origin. Internal structures were examined using real-time microradiography (RTX) and X-ray computed microtomography (µ-CT). The authors also recorded the samples' UV-Visible, Raman, and photoluminescence (PL) spectra. 

The results appear to indicate that these NBC pearls were cultured in Pinctada margaritifera mollusks, or at least were formed from mantle that incorporated the genes of this mollusk. The authors note that the various spectra and internal structures recorded in the study will provide valuable reference data on NBC pearls.