北海南珠的微观结构及成分研究

Study on the microstructure and composition of South-Pearl in Beihai,Guangxi

影响南珠质量的因素研究将有利于养殖高质量的海水珍珠。利用扫描电镜、X射线衍射仪、热重分析仪、原位微量激光烧蚀-电感耦合等离子体质谱仪等仪器设备,对广西北海南珠的微观结构和物质组成进行了测试研究。结果表明,北海南珠的无机物主要为文石和少量的方解石,优质珍珠中文石板片的厚度均匀、排列整齐,文石的质量分数占无机物的88.0%以上,残次珍珠中文石板片的厚度极不均匀,层状结构不明显,文石的质量分数只占无机物的79.1%;优质珍珠中有机质的质量分数只有1.28%,残次珍珠中有机质的质量分数却高达7.07%;在化学成分中,优质珍珠的Ca含量明显高于残次珍珠,而残次珍珠中Mg、P、Mn、Sr等微量元素成分的含量相对较高,且残次珍珠表面黑色凸起处含有较高的Mg、S、Zn等元素。分析认为,珍珠中文石含量越多,晶体排列有序度越高,珍珠光泽就越好;珍珠层中有机物含量过高反而会降低珍珠的质量;珍珠中微量元素成分及其含量对碳酸钙的成核、结晶生长都有重要作用,Mg、Fe含量增大可能会阻碍文石的结晶和板片的形成,导致南珠表面形成杂色、突起等瑕疵。

The study of factors affecting the quality of south-pearls will be beneficial to the cultivation of high quality seawater pearls.The microstructure and material composition of south-pearls from Beihai,Guangxi were tested and studied by using scanning electron microscope,X-ray diffractometer,thermogravimetric analyser,in situ micro laser ablation-inductively coupled plasma mass spectrometer and so on.The results show that the inorganic substances of the South-Pearls from Beihai,Guangxi are mainly aragonite and a small amount of calcite,the thickness of plate-structured aragonite in the high-quality pearls is uniform and well arranged,and the mass fraction of aragonite accounts for more than 88.0%of the inorganic substances,while the thickness of plate-structured aragonite in the defective pearls is extremely uneven,the laminar structure is not obvious,and the mass fraction of aragonite only accounts for 79.1%of the inorganic substances;the mass fraction of the organic matter in the high-quality pearls is only 1.28%,but the mass fraction of organic matter in the defective pearls is as high as 7.07%.In the chemical composition,the Ca content of high-quality pearls is significantly higher than that of defective pearls,while the content of trace element components such as Mg,P,Mn,Sr in defective pearls is relatively high,and the black bumps on the surface of the defective pearls contain a high level of Mg,S,Zn elements.We analyze that the more aragonite content in pearls,the higher the degree of orderliness of crystal arrangement,the better the pearl luster;the high content of organic matter in the pearl layer will reduce the quality of the pearl;trace element components and their content in pearls play an important role in the nucleation and crystalline growth of calcium carbonate,and the increased content of Mg and Fe may impede the crystallization of plate-structured aragonite,which will lead to formation of mottled color,protrusion and other defects on the surface of the south-pearl.