Assessment of Pearl Quality by UV-Vis Spectroscopy (CAT#: STEM-MB-0900-WXH)

Introduction

Pearl quality is determined by five primary factors: lustre, color, shape, surface contour and size. Many of these characteristics are subjective and may depend on individual perceptions. Pearl grading is also labor intensive and requires skill and experience. A pearl grader has to be able to quantify and collate all visual observations and allocate each pearl to a defined grading level. However, techniques are available that may assist in reducing subjectivity in assessing some aspects of pearl quality. As UV-Vislight passes through, or is reflected by, a material, specific groups of wavelengths are absorbed and the remaining light is reflected and interpreted by the eye as color. Based on the wavelengths detected within the ultraviolet and eye-visible regions, UV-Vis spectroscopy can rapidly identify chemical properties and color pigments in a non-destructive way. Because pearl color and overtone is determined by the way in which light is reflected through the various outer layers of nacre forming the pearl, this technique has obvious potential application in quantification of pearl color.