Last year the New York laboratory reported on the use of shell as a pearl imitation (Summer 2014 Lab Notes, pp. 153–154) and the improper nomenclature applied by those marketing it. We decided to delve deeper and investigate the nature of the shell beads used in such imitation pearls following correspondence with Dr. Henry A. Hänni, who previously reported on this issue (see Summer 2004 Gem News International, p. 178, and references within).
After removing the outer coating on one of the imitation pearls by immersing it in acetone, we observed a banded white bead (figure 1, left). Magnification revealed fine and subtle flame structures (figure 1, right), indicating the bead was most likely fashioned from the shell of a Tridacna (giant clam) species.
All species of the Tridacnidae family are currently listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Some species, such as Tridacna gigas , are more vulnerable than others, such as Tridacna squamosa or Tridacna maxima . These large saltwater clams can have heavy shells fluted with multiple folds (figure 2) and colorful mantles. Their natural habitats lie in the warm marine waters of the Indo-Pacific, a fragile region that has been heavily impacted by human activities.
These beautiful marine animals are commonly harvested from their natural habitats or aquaculture farms for food ( Center for Tropical and Subtropical Aquaculture Publication No. 114 , University of Hawaii), and their shells are fashioned into beads or ornaments that are prized by some cultures. Despite their protection under CITES, these shell products are readily available on the Internet and often very inexpensive (figure 3). Imitation shell “pearls” fashioned from these endangered and protected mollusks do not offer any obvious advantages over common freshwater mussel shells, and it is extremely difficult to identify the exact Tridacna species or whether the mollusks were farmed or harvested from the wild. We urge manufacturers to stop using Tridacna shell beads when producing imitation pearls.
Last year the New York laboratory reported on the use of shell as a pearl imitation (Summer 2014 Lab Notes, pp. 153–154) and the improper nomenclature applied by those marketing it. We decided to delve deeper and investigate the nature of the shell beads used in such imitation pearls following correspondence with Dr. Henry A. Hänni, who previously reported on this issue (see Summer 2004 Gem News International, p. 178, and references within).
After removing the outer coating on one of the imitation pearls by immersing it in acetone, we observed a banded white bead (figure 1, left). Magnification revealed fine and subtle flame structures (figure 1, right), indicating the bead was most likely fashioned from the shell of a Tridacna (giant clam) species.
All species of the Tridacnidae family are currently listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Some species, such as Tridacna gigas , are more vulnerable than others, such as Tridacna squamosa or Tridacna maxima . These large saltwater clams can have heavy shells fluted with multiple folds (figure 2) and colorful mantles. Their natural habitats lie in the warm marine waters of the Indo-Pacific, a fragile region that has been heavily impacted by human activities.
These beautiful marine animals are commonly harvested from their natural habitats or aquaculture farms for food ( Center for Tropical and Subtropical Aquaculture Publication No. 114 , University of Hawaii), and their shells are fashioned into beads or ornaments that are prized by some cultures. Despite their protection under CITES, these shell products are readily available on the Internet and often very inexpensive (figure 3). Imitation shell “pearls” fashioned from these endangered and protected mollusks do not offer any obvious advantages over common freshwater mussel shells, and it is extremely difficult to identify the exact Tridacna species or whether the mollusks were farmed or harvested from the wild. We urge manufacturers to stop using Tridacna shell beads when producing imitation pearls.