The Keshi Pearl Issue

Nick Sturman (Directorate of Precious Metals and Gemstone Testing, Ministry of Industry and Commerce, Bahrain) writes:

The word Keshi has traditionally been used to describe small natural saltwater pearls (seed pearls) as well as similarly sized pearls that resulted as a byproduct of the Japanese cultured pearl industry. Nowadays, the term is predominantly used to describe cultured pearls with sizes well above those that would be considered seed-like. Hence, Keshi is now used generically to describe any pearl byproduct without a bead nucleus that is produced by the culturing process regardless of the ocean in which the pearl farm is located.

The contentious aspect of Keshi cultured pearls revolved around the following questions: Can gemological laboratories differentiate between all Keshi cultured pearls and natural pearls? In our opinion and experience, the answer to this question is no. Some Keshi cultured pearls are instantly recognizable by their overall visual appearance, and their cultured origin can be further validated by their internal structural features, as revealed by X-radiography. In other cases, laboratories are faced with an identification issue that may either straightforward (i.e., the X-radiographic structures are quite distinct, classifying them as tissue-nucleated cultured pearls) or difficult (i.e., they exhibit natural-appearing structures).

Quantity testing of Keshi cultured pearls (i.e., in rows, necklaces, or parcels) may be thought of as less complicated because the test results are based on those samples that show the most evident structures. However, this is not always true, and we often have to issue mixture, majority/minority, or even natural reports on parcels of what appear to be Keshi cultured pearls. When individual pearls are submitted (i.e., for a full test as opposed to batch testing), the situation may be trickier since only the structure of a single sample, and not a group of pearls, is available to the gemologist. If the structure appears natural by X-radiography, then a natural report can be issued. In our experience, individual pearls with internal structures that are undoubtedly natural will pass as such in most, if not all, laboratories.

We do not have a solution to the differences in opinion that exist in the trade regarding what constitutes a Keshi pearl, and believe that a good deal of research still needs to be carried out on the subject.