Heart-Shaped Golden South Sea Cultured Pearl
The heart shape has been a worldwide symbol of love and romance for centuries. GIA’s New York laboratory recently received a golden-colored heart-shaped pearl pendant that drew our attention. The pearl was reportedly produced in the Philippines, which is a major source of golden South Sea cultured pearls. Upon routine gemological and advanced instrumental examination—including microradiography, ultraviolet/visible spectroscopy, manganese and strontium contents from energy-dispersive X-ray fluorescence, and reaction to long-wave UV—we concluded that it was an atypical bead cultured pearl from the Pinctada maxima species, commonly known in the trade as a South Sea cultured pearl (figure 1), and its heart shape and golden color were entirely natural.
Unlike the traditional bead cultured pearls typically nucleated with spherical shell bead nuclei, a heart-shaped bead nucleus was used in this pearl to achieve its unique shape. Hence, it was described as an “atypical bead” cultured pearl (aBCP) according to GIA’s pearl identification terminology. Real-time microradiography (RTX) and X-ray computed microtomography (CT) clearly revealed the internal structure of a heart-shaped bead nucleus (figure 2). The nacre coverage, averaging 0.80 mm thick, was evenly distributed all around the nucleus, demonstrating that the heart shape of the pearl was consistent with the shape of the nucleus. Magnification revealed no signs of surface working or treatment, suggesting the pearl was in its original form after harvest. It displayed a strong orangy yellow color that is highly sought after among South Sea pearls. Ultraviolet/visible reflectance and photoluminescence spectroscopy further confirmed its natural color origin (C. Zhou et al., “Update on the identification of dye treatment in yellow or ‘golden’ cultured pearls,” Winter 2012 G&G, pp. 284–291).
Although this was not the first time a heart-shaped pearl has been examined in the lab, it is very rare to see a whole pearl with such a perfect non-round cultured shape. Previous submissions have either been identified as mabe pearls (assembled cultured blisters) or have had poorly defined heart shapes. Mabe pearls are not considered whole pearls and often possess a thin nacre dome top (Fall 2021 Gem News International, pp. 277–279). Due to the thin nacre, their shape is easier to control. Therefore, fancy-shaped nuclei are commonly used in mabe pearls.
Many atypical bead cultured pearls have been studied and examined over the years at GIA (“Atypical ‘beading’ in the production of cultured pearls from Australian Pinctada maxima,” GIA Research News, February 13, 2017; Fall 2022 Gem News International, pp. 378–380). However, the majority of the end products are very different from the original shape of the nuclei. This remarkable use of an atypical bead nucleus to achieve a perfect shape in a cultured pearl suggests recent improvements in pearl culturing techniques.
