Internal Structures of Known Pinctada Maxima Pearls: Natural Pearls from Wild Marine Mollucks

Abstract

P earls are biogenic gem materials that may form naturally without human intervention, or with assistance from humans in a culturing process. Natural and cultured pearls often display similar external appearances and occasionally cannot be differentiated without examining their internal structures. Over the last century, scientists and gemological laboratories have used film X-radiography and digital real-time microradiography (RTX) to reveal these interior growth patterns (

Internal Structures of Known Pinctada Maxima Pearls: Cultured Pearls from Operated Marine Mollusks

“…Most of the RTX images of the samples contained a dark gray (more radiolucent) or light gray (more radiopaque) core at the center of the concentric structures, similar to some observations in natural P. maxima pearls (Homkrajae et al, 2021). However, the core in each of these samples differed in size and form from those observed in the natural pearls.…”

“…This is confirmed by the sample's provenance. Although an oval core has been observed in a natural pearl (Homkrajae et al, 2021), the authors believe that the spindle-shaped cores in samples 1-9 through 1-11 have only been reported in NBC pearls.…”

“…Moreover, some natural pearls also possess structures that resemble those observed in NBC pearls. These can be challenging to correctly identify, especially when the pearls are submitted without any provenance (Scarratt et al, 2012;Sturman et al, 2019;Homkrajae et al, 2021). To better understand the characteristic internal features of P. maxima NBC pearls, as well as BC pearls with associated additional surface growths, the authors studied a selection of NBC and BC pearls grown in cultured pearl sacs and harvested directly from the gonads of operated mollusks.…”

“…The various types of internal structure recorded in these samples are presented here, the second in a series of three articles that investigate the internal structures of P. maxima pearls produced by different growth mechanisms. The natural pearls retrieved directly from unoperated wild mollusks were covered in Homkrajae et al (2021), and the final article will address pearls that form in the mantle area or adductor muscle, or are found attached to the shell of operated wild and hatchery mollusks.…”

“…Photomicrographs were obtained to show certain features in greater detail using a Nikon SMZ18 stereomicroscope with an SHR Plan Apo 1× objective lens and NIS-Elements imaging software. As with Homkrajae et al (2021), the purpose of this work was only to investigate the samples' internal characteristics.…”