广绿玉玉石的矿物学研究

 广绿玉产于广东省广宁县，是一种富有特色的珍贵玉石材料。对绿、白、黄、黑等4类典型广绿玉原料，采用X射线粉末衍射、扫描电镜、红外光谱、差热分析、电子探针等多种方法，对玉石的全岩物相、主矿物显微形貌、矿物化学及晶体结构等进行了分析。结果表明，广绿玉主要由2M1型绢云母组成，部分品种含有绿泥石和石英等。乙二醇饱和处理X射线粉末衍射和红外光谱分析显示绢云母结构中不含蒙脱石间层；差热分析显示玉石在中温区吸热谷的脱羟极值温度大于600 ℃，与水云母明显不同；扫描电镜显示绢云母类单矿物的微形貌多呈鳞片状，矿物排列组合沿长轴顺层穿插和定向交织，表现为叠层状或鳞片交织状微结构；电子探针成分分析表明绢云母矿物化学成分中Si、K、Al、Cr等含量较高，部分属含铬绢云母亚类，Cr可能是绿色和白色广绿玉的主要致色元素。

Study on Mineralogy of Guangning Jade

The Guangning jade is a precious type of Chinese jades, which is found in Guangning county, Guangdong province. Four types of different colored jade stones were sampled from a jade deposit. Their mineralogical characteristics were analyzed using XPD, SEM, DTA, IR and EMPA techniques. The Guangning jade is mainly composed of 2M1 sericite, and secondly chlorite. Both XPD and IR results indicate daunialite does not exist in the crystal structure of sericite. The analysis of DTG shows that the dehydroxylation tempreture of samples is beyond 600 ℃, which is different from hydromica. The micro texture of sericite shows flake shaped, and the minerals arrange along the long axis of crystal, interleaved by each other, showing overlapped and flake interleaved microstructure. The EMPA suggests that sericite is rich in Si、K、Al and Cr. Those rich in Cr can be grouped into Cr bearing sericite.