Recently, GIA’s Mumbai laboratory received a light gray near-round pearl for identification, weighing 13.12 ct and measuring 14.06 × 13.75 × 12.76 mm. Externally, the surface of the pearl displayed an uneven texture with white blotches and had an opening plugged with a small light brownish gray near-round seed pearl (figure 1). Under higher magnification, the surface of both the pearl and the seed pearl revealed typical nacreous structures with overlapping aragonite platelets. The presence of aragonite was further confirmed by Raman spectroscopy using 514 nm laser excitation.
Chemical analysis of the pearl using energy-dispersive X-ray fluorescence revealed no traces of manganese and a strontium level of 1535 ppm. Both the pearl and the seed pearl showed inert reactions when exposed to X-ray fluorescence, confirming their saltwater origins.
Real-time X-ray microradiography (RTX) and X-ray computed microtomography (μ-CT) images both revealed a distinct light gray demarcation of nacre surrounding a large dark gray area of an unidentified radiolucent foreign material within the large pearl (figure 2). The unidentified material contained darker gray blotches of gas bubbles. The seed pearl was seen resting atop the filling material, suggesting it was intentionally used to seal the pearl’s opening. The drilled seed pearl exhibited a central core surrounded by fine growth arcs similar to those observed in natural pearls.
Two possible scenarios arise regarding the pearl’s formation. The first suggests the use of an atypical bead for culturing the pearl, differing from the conventional freshwater shell bead. Numerous experimental attempts have explored alternative materials as bead nuclei, including organic nuclei or, as in this case, an unknown material similar to synthetic substances such as plastic or resin (L. Cartier and M.S. Krzemnicki, “New developments in cultured pearl production: Use of organic and baroque shell nuclei,” Australian Gemmologist, Vol. 25, No. 1, 2013, pp. 6–13; S.C. Shih and P. Cevallos, “Polystyrene nucleus in a freshwater cultured pearl,” Journal of Gemmology, Vol. 39, No. 5, 2025, pp. 445–447). The second scenario could be that it was filled after the formation of the pearl. The latter scenario appears more plausible due to the presence of gas bubbles within the void and along the demarcation. This intention to mask the unidentified foreign material with the seed pearl further complicated identification.
Identifying the nature of such a pearl can be challenging, whether it is an atypical bead cultured pearl or a filled non-bead cultured pearl. While the possibility of alternative culturing methods cannot be overlooked, the characteristics observed in the examined pearl suggest that it is not of natural origin but rather a product of a cultured formation. Further analysis is required to understand the composition of the unidentified foreign material and to reach a more conclusive identification of the pearl.
Karan Rajguru is a gemologist, and Roxane Bhot Jain is manager of pearl, melee, and AGSI technical and market development, at GIA in Mumbai. Abeer Al-Alawi is a consultant to GIA. Artitaya Homkrajae is manager of pearl identification at GIA in Carlsbad, California.
Recently, GIA’s Mumbai laboratory received a light gray near-round pearl for identification, weighing 13.12 ct and measuring 14.06 × 13.75 × 12.76 mm. Externally, the surface of the pearl displayed an uneven texture with white blotches and had an opening plugged with a small light brownish gray near-round seed pearl (figure 1). Under higher magnification, the surface of both the pearl and the seed pearl revealed typical nacreous structures with overlapping aragonite platelets. The presence of aragonite was further confirmed by Raman spectroscopy using 514 nm laser excitation.
Chemical analysis of the pearl using energy-dispersive X-ray fluorescence revealed no traces of manganese and a strontium level of 1535 ppm. Both the pearl and the seed pearl showed inert reactions when exposed to X-ray fluorescence, confirming their saltwater origins.
Real-time X-ray microradiography (RTX) and X-ray computed microtomography (μ-CT) images both revealed a distinct light gray demarcation of nacre surrounding a large dark gray area of an unidentified radiolucent foreign material within the large pearl (figure 2). The unidentified material contained darker gray blotches of gas bubbles. The seed pearl was seen resting atop the filling material, suggesting it was intentionally used to seal the pearl’s opening. The drilled seed pearl exhibited a central core surrounded by fine growth arcs similar to those observed in natural pearls.
Two possible scenarios arise regarding the pearl’s formation. The first suggests the use of an atypical bead for culturing the pearl, differing from the conventional freshwater shell bead. Numerous experimental attempts have explored alternative materials as bead nuclei, including organic nuclei or, as in this case, an unknown material similar to synthetic substances such as plastic or resin (L. Cartier and M.S. Krzemnicki, “New developments in cultured pearl production: Use of organic and baroque shell nuclei,” Australian Gemmologist, Vol. 25, No. 1, 2013, pp. 6–13; S.C. Shih and P. Cevallos, “Polystyrene nucleus in a freshwater cultured pearl,” Journal of Gemmology, Vol. 39, No. 5, 2025, pp. 445–447). The second scenario could be that it was filled after the formation of the pearl. The latter scenario appears more plausible due to the presence of gas bubbles within the void and along the demarcation. This intention to mask the unidentified foreign material with the seed pearl further complicated identification.
Identifying the nature of such a pearl can be challenging, whether it is an atypical bead cultured pearl or a filled non-bead cultured pearl. While the possibility of alternative culturing methods cannot be overlooked, the characteristics observed in the examined pearl suggest that it is not of natural origin but rather a product of a cultured formation. Further analysis is required to understand the composition of the unidentified foreign material and to reach a more conclusive identification of the pearl.
Karan Rajguru is a gemologist, and Roxane Bhot Jain is manager of pearl, melee, and AGSI technical and market development, at GIA in Mumbai. Abeer Al-Alawi is a consultant to GIA. Artitaya Homkrajae is manager of pearl identification at GIA in Carlsbad, California.
