Application of UV-VIS Diffuse Reflectance Spectrum, Raman and Photoluminescence Spectrum Technology in Nondestructive Testing of Yellow Pearl

Using Ultraviolet-visible ( UV-Vis) diffuse reflectance spectrum, Raman and Photoluminescence (FL) spectrum technology, the color properties of pearls with different sizes and different shades of golden saturation on the market are explored. The results show that yellow pearls can be initially divided into types I and II based on the UV-VIS reflection spectrum characteristics. The corresponding spectra of type I pearls have absorption bands at (360 +/- 5) nm and weak absorption peaks or shoulders at (420 +/- 10) nm. These pearls are common in the current pearl market, pigments in their own structure caused the color of which. Other golden yellow pearls belong to Type II except for type I. The corresponding reflection spectral absorption band's main peak is in the range of 330-430 nm. However, some type II samples have no obvious absorption or only weak absorption shoulder at 280-600 nm. Raman spectroscopy was further used to detect the type II pearl. The treated type II yellow pearls displayed strong fluorescence peaks in the range of 150 similar to 1 000 cm(1) when the excitation intensity was low, and the intensity of the fluorescence peaks was significantly higher than the characteristic peak at about 1 086 cm (1) of aragonite. Meanwhile, the PL spectra of the treated type II pearls also showed that fluorescence intensity increased significantly in the range of 500-600 nm. In addition, the above abnormal fluorescence and exotic characteristic peaks in the Raman and PL spectra of the type II pearls can be used as evidence for treatment. The research provides theoretical and technical support for the coloring formation of golden pearls and the identification of imitation pearls. Meanwhile, it has important reference significance for Raman spectroscopy in detecting and identifying other kinds of precious jade, especially organic gems.