Dual-modal identification of jadeite based on optical coherence tomography images and Raman spectral features

Abstract

Low-quality jadeite is often subjected to bleaching, filling, and dyeing to improve its texture and consequently increase its value. In this study, natural jadeite, bleached and filled jadeite, and dyed jadeite were investigated by combining Raman spectroscopy and optical coherence tomography (OCT). The results show that jadeite composition can be identified from Raman peaks around 205, 377, 700, and 1040cm−1. The presence of epoxy filler can be detected from Raman peaks at 1113, 1187, and 1609cm−1, among which the features of 1113 and 1609cm−1 are particularly significant. Dyed jadeite exhibits a pronounced fluorescence background in its Raman spectrum due to the injected dye. After noise reduction, texture vectors representing the texture of bleached or dyed jadeite can be obtained from OCT images. These vectors differ from the corresponding texture vector of natural jadeite. Most processed jadeites have relatively low texture vector intensities due to particle reduction and texture damage during processing. However, the texture vector strengths of jadeites can be increased through internal silting.