Feature

A Study on Improving the Surface Appearance of Low-Quality Pinctada maxima Bead Cultured Pearls


A row of five low-quality bead cultured pearls.
Five low-quality Pinctada maxima bead cultured pearls showing dull surface lustres, yellowish brown imperfections and residual organic-rich features. Photo: Nuttapol Kitdee

Pearls are evaluated based on seven value factors, which include size, shape, colour, lustre, surface, nacre quality and matching. Manufacturers often increase the perceived value of low-quality pearls by improving the appearance of one or more of these factors. In this study, the Bangkok laboratory examined five low-quality bead cultured pearls sourced directly from a local pearl factory and characterised their features before and after processing. Real-time microradiography (RTX), energy dispersive X-ray fluorescence (EDXRF) and Raman spectroscopy were utilised to check potential differences in nacre thicknesses, fluorescence reactions, and chemical and mineral compositions.
 
The results are available in a study titled “A Study on Improving the Surface Appearance of Low-Quality Pinctada maxima Bead Cultured Pearls”. The authors concluded that methods used to improve the appearance of low-quality pearls were not always successful, and the level of success might not be economically viable for manufacturers.

Nanthaporn Nilpetploy is a senior staff gemmologist, Kwanreun Lawanwong and Promlikit Kessrapong are analytics technicians, and Areeya Manustrong is a staff gemmologist in the pearl department at GIA in Bangkok. Nicholas Sturman is a consultant to GIA based in Bangkok.