淡水养殖珍珠棱柱层的微结构形貌特征

通过x射线粉晶衍射（XRD）、场发射扫描电镜（FE—SEM）对不同颜色的淡水养殖珍珠的微结构进行较系统研究。结果表明，质优的珍珠其矿物相为文石，未见有方解石或球文石相，不同颜色的珍珠质层文石板片的厚度存在较大差异。质量较好的珍珠中接近珍珠核心区域存在棱柱层，该棱柱层由众多的纤维或条带状文石结晶体聚集而成，其中文石纤维或条带的定向近平行于珍珠层文石板片。此外，首次发现在淡水养殖珍珠的棱柱层中文石纤维与板片结晶体交替出现，同时初步建立了一种新的淡水养殖珍珠的内部结构模型。

Microscopic morphology of prismatic layers of freshwater cultured pearl

The microscopic morphology of the internal structure of freshwater cultured pearl with different colors were investigated by X- ray diffraction （XRD） and field emission-scanning electronic microscope （FE-SEM）. Results clearly reveal that aragonite is found in high quality freshwater cultured pearls, but calcite and vaterite are not found, and the thickness of aragonite sheet in nacreous layer is not the same to pearls with different colors. The prismatic layer is near to the nucleus of the high quality pearls, which is made of a number of cylindrical or banded aragonite fibers. The fibers are oriented nearly parallel to the aragonite sheet. In addition, it is firstly observed that the aragonite fiber and sheet appear alternately in prismatic layer. Meanwhile, a modified model of the internal structure of freshwater cultured pearls is firstly established.