Reserach on Raman Spectra of Organic Ingredients on Colored Pearls
HU Yang1, FAN Lu-wei2*, HUANG Yi-lan3
1. Gemmological Institute, China University of Geosciences, Wuhan 430074, China 2. Yifu Museum, China University of Geosciences, Wuhan 430074, China 3. Journal of Gems & Gemmology, China University of Geosciences, Wuhan 430074, China
Abstract：Based on the visible spectra and Raman spectra test of a variety of colored pearls samples to study the relationship between the organic component and the pearl’s color was studied. The study results show that both the freshwater and seawater pearls exhibit strong characteristic peaks in 1 121～1 132 and 1 506～1 524 cm-1 range, which is respectively attributed to the C—C and CC stretching vibration; the peak intensity in 1 117～1 132, 1 502～1 524 and 2 000～3 500 cm-1 range increases as the color deepens, which is closely related to the pearl’s color; The peak in the 1 475～1 575 cm-1 range is divided into 8～10 secondary peaks of purple freshwater pearl and deep orange seawater pearl. The number of CC double bonds is N=9～27 and N=7～27 respectively after calculation. Polyene compound of different varieties and content could be the reason for the pearls’ color.
Key words：Pearl;Organic color caused;Visible spectroscopy;Raman spectroscopy
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