池蝶蚌贝壳及其珍珠的微结构表征

Microstructure of Hyriopsis Schlegeli Shells and Its Pearls

以江西抚州的池蝶蚌贝壳及其珍珠为主要研究对象,采用宝石显微镜、偏光显微镜和扫描电子显微镜观察其表面特征和微结构。结果表明,池蝶蚌贝壳纵断面的总体结构为:表壳层—棱柱层—珍珠层,部分贝壳出现多层复杂的生长组构可能是由于贝壳的生长间断引起。珍珠层呈现"砖墙"结构特征,由有机质将文石小板片如"砌墙"般垒积而成。值得注意的是,在池蝶蚌贝壳及其珍珠的珍珠层表面出现螺旋状纹理,这种现象在其它的淡水珍珠(如三角帆蚌贝壳及其珍珠)中极为少见。采用扫描电子显微镜观察螺旋状纹理发现,单个的螺旋生长结构由半封闭的圈层构成,因此认为,其属于一种层状堆积的变异表现形式;池蝶蚌珍珠中部分有核珍珠的结构特征自内向外表现为:珠核—珠核表面初始生长层—珍珠层。珠核表面初始生长层中的文石呈不规则球粒状无序堆积,显示出快速生长的结构特征。

By means of gemmological microscope, polarizing microscope and scanning electron microscope, the special surface characters and microstructure of the Hyriopsis schlegeli shells and its pearls from Fuzhou,Jiangxi Province,are observed. The results indicate that the main characters of the vertical section of the shells are periostracum-prismatic layer-nacreous layer. Some of the shells behave as a multilayer intricate complex growing structure,which could be due to the discontinuous growing of the shells. The structure of nacreous layer is characterized as a form of ＂brick wall＂, laying the ＂bricks＂ with organic matter and aragonite slices. To be noticed that the spiral grains on the surface of nacreous layer of Hyriopsis schlegeli shells and its pearls are rarely found in other fresh water cultured pearls. When scanning the spiral grains on the special surface by using scanning electron microscope, it is found that a single spiral line is constituted by semi-closed circles, accordingly, it could be a variant form of layered deposits. By means of SEM, it is found that the characteristic structures of some nucleated pearls behave from inner to outside：nucleus-initial growth layer - nacreous layer. The aragonites in the initial growth layer deposit randomly in the form of irregular spherulhes, which indicates the character of fast growth.