青海软玉的岩石矿物学特征

Petrological and Mineralogical Characteristics of Qinghai Nephrite

对采自青海东昆仑三岔口软玉矿区的样品进行了显微硬度、扫描电镜、X射线粉晶衍射物相定性和结晶度等分析,并将分析结果与新疆和田软玉进行了对比研究,发现青海软玉普遍显示出硬度较高、透闪石含量稍低、结晶度偏高的特点;透闪石主要呈毛毡状交织结构、显微纤维结构和显微片状结构,定向性普遍较好。对比两地软玉矿区的矿床地质特征,发现青海软玉成矿母岩相对贫Mg、Si而富Ca,动力改造相对较弱,成矿温度较高,这是造成两地所产软玉在上述岩石矿物学特征上巨大差异的根本原因;也是造成青海软玉透明度偏高、油润度不足的根本原因。

The mineral phases of Qinghai nephrite are analyzed through the microhardness test, scanning electron microscopic observation, qualitative analysis by X-ray powder diffractometry and crystallinity analysis. Compared with the Xinjiang Hetian nephrite, some characteristics of Qinghai nephrite, such as higher hardness, higher crystallinity, lower content of tremolite, were found. The Qinghai nephrite mainly appears as the felt-like texture, the micro-fibrous texture and the micro-leaf-like texture with excellent orientability. Qinghai nephrite also presents the distinct deposit geological characteristics, such as lack of Mg and Si but abundant of Ca in its parent deposit rocks, weaker dynamic reconstruction but higher mineralizing temperature. It is believed to be the ultimate cause for differences in petrological and mineralogical characteristics of Qinghai nephrite from that of Xinjiang nephrite. And it is also one of the reasons why Qinghai nephrite always shows higher transparency and lower oil luster.