Feature Gems & Gemology, Spring 2000, Volume 36, No. 2

Characteristics of Nuclei in Chinese Freshwater Cultured Pearls

Kenneth Scarratt, Thomas M. Moses, and Shigeru Akamatsu

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There has been considerable debate in the gem trade concerning the nucleation procedures being used to grow large round Chinese freshwater cultured pearls (FWCPs). Of particular concern are claims that most of these cultured pearls are nucleated by reject mantle-tissue-nucleated FWCPs, and that such a product would be difficult to separate from normal tissue-nucleated cultured pearls and in some cases from natural pearls. However, field research indicates that many Chinese growers are currently using larger mussels (Hyriopsis cumingi), combined with new tissue-insertion techniques, to grow larger, better-shaped FWCPs. For this study, X-radiographs of approximately 41,000 Chinese freshwater cultured pearls from dozens of farms were examined, and 10 samples were sectioned. All showed evidence of mantle tissue nucleation only; the presence of a bead, whether shell or a tissue-nucleated FWCP, would be identifiable by distinctive features seen in the X-radiograph.