YANG Lei¹, OUYANG Qian-Qian², LI Si-Dong¹, CHEN Jin³, HE Dong-Ning⁴

（1. College of Science, Guangdong Ocean University, Zhanjiang 524088, China;
2. Guangdong Provincial Key Laboratory of Aquatic Product Processing and Safety, Key Laboratory of Advanced Processing of Aquatic Products of Guangdong Higher Education Institution, College of Food Science and Technology, Guangdong Ocean University, Zhanjiang 524088, China;
3. Jia Hui Pearl Co. of Zhanjiang, Zhanjiang 524001, China;
4. Agricultural Product Processing Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang 524001, China）

Abstract: This paper reports the influence of metallic impurities on the microstructure of pearls. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to analyze trace elements in the microstructure of the surface and longitudinal section of the pearls. The prismatic layer and nacreous layer of the pearls were analyzed in situ by Raman spectroscopy using a 785 nm excitation wavelength. Trace metallic elements in good and inferior quality pearls were analyzed with plasma emission spectrometer (ICP). Aragonite in pearl’s prismatic layer and impurities present affect the normal mineralization process in inferior pearls. The Mg, Fe, Zn, Mn and P contents in inferior pearls are higher than those of higher quality pearls. The degree of ordered arrangement of aragonite crystals on the surface of inferior pearls is lower than that on the surface of good quality pearls. The denser is ordered arrangement and the thinner the thickness of the layering the better the quality will be. The structure of the prismatic layer in good quality pearls is also denser than that in inferior pearls. Also, the aragonite tablets and the prismatic layer in good quality pearls are thinner than those in poor quality pearls.

Key words: pearl; seawater pearl; metal ion; SEM