不同体色淡水养殖珍珠的结构特征研究

Study on the Structure of Fresh-water Cultured Pearls with Different Body Colors

本文利用拉曼光谱仪和高分辨扫描电子显微镜对四种不同体色的淡水养殖珍珠进行了测试和观察,发现不同体色珍珠的表面和剖面断裂面形貌都不同。白色和黄色珍珠表面具有相对比较整齐的生长台阶,而紫罗兰色和紫色珍珠表面的生长台阶杂乱无章。尤其是紫色珍珠,不仅生长台阶不平行整齐,而且存在台阶聚并现象以及缺陷。对于珍珠剖面的断裂面的观察,发现白色和黄色珍珠的文石板片层厚度约为200～400 nm;而紫罗兰色和紫色珍珠的约为100～300 nm,且排列更致密。进一步对剖面进行EDTA腐蚀后发现,珍珠文石板片层之间的CaCO3首先被腐蚀,之后在片层之间留下网格状的有机质;紫罗兰色珍珠的最易被腐蚀,而紫色珍珠最难被腐蚀,由此判断紫色珍珠的结构致密性明显优于其他颜色珍珠。

Four fresh-water cultured pearls with different colors were measured and observed by Raman spectroscopy and high resolution scanning electron microscopy.The results showed that the morphologies of the exterior surface and fracture profile for the four pearls showed different characteristics.The surface of white and yellow pearls presents trim growth steps,but the growth steps of violet and purple pearls are disorder.Especially for the purple pearl,not only the growth steps are irregular,but also the surface owns more bunching steps and defects than others.As for the fracture surface observation,we found that the aragonite platelets thickness of white and yellow pearls was about 200-400 nm wheareas the aragonite lamina of violet and purple pearls ranked more densely and the thickness was about 100-300 nm.After etching by EDTA,it was discovered that there is organic matrix left between the lamina.The violet pearl was the easiest one to be etched by EDTA,and the purple pearl was the most difficult one,so it can be concluded that the purple pearl was very dense.That's why the purple pearl owns the best luster in the situation of bad exterior surface.