A pearl identification challenge

Nacreous pearls are usually found in saltwater (SW) or freshwater (FW) environments, yet there are some reports of pearls originating from a brackish environment. Likewise, nacreous pearls may form naturally or by human manipulation (bead and non-bead cultured), but in some cases the origin is hard to prove and professional opinions are not always unanimous. Two pearls were examined by the authors, who were in the unique situation of being unable to positively identify either their origin (natural or cultured) or growth environment (FW versus SW). This in turn had a direct impact on the ability to determine which mollusk produced the pearls, a factor that would have helped answer the former two questions. It is very rare to find pearls for which all three of these criteria are in doubt, as usually it is straightforward to determine at least two of them. The results of this study illustrate the challenges that laboratories sometimes face when testing pearls.