Two Brown Non-nacreous Natural Pearls with Embossed Surface Features.

The article focuses on the study of non-nacreous natural pearls, particularly those from Pinctada species, highlighting their internal structures, surface features, and fluorescence properties. Two brown non-nacreous pearls from Pinctada radiata collected near Sitra Island, Bahrain, exhibited unusual embossed surface ridges and organic-rich concentric internal structures revealed by RTX and micro-CT imaging; environmental pollution in the area is suggested to influence these pearl characteristics. Additionally, the EXA fluorescence spectrometer was used to quantify photoluminescence in untreated natural and cultured pearls from Pinctada species, showing consistent yellowish green fluorescence under long-wave UV excitation. The findings underscore the complexity of pearl formation and the need for further research on environmental and biological factors affecting non-nacreous pearls.