翡翠的皮壳组成及其与内部玉石质量关系初步研究

在对广东南海平洲、广州花都国际翡翠展销会等翡翠原料集散地大量现场考察的基础上，选取了具有黄色色调、白色和灰黑色皮壳的翡翠原石样品，经肉眼和偏光显微镜观察、X射线粉末衍射和电子探针测试，研究了不同颜色系列翡翠原石皮壳的矿物组成和化学成分特征。结果表明，不同颜色翡翠皮壳的主要矿物均为硬玉，次要矿物则有所不同。黄色皮壳含高岭石、三水铝石、软锰矿和赤铁矿等，白色皮壳含高岭石和水钙铝榴石，黑色皮壳则含高岭石和绿泥石类矿物。与内部玉石成分相比，皮壳中的主要化学成分硼（Na2O）和w（SiO2）有所降低，而w（CaO）和w（MgO）及Fe的质量分数则相对增加；黄色皮壳翡翠中Fe的质量分数越高，则皮壳的黄色色调越深，但皮壳的化学成分受环境影响较大，难以用于判断其内部玉石质量。仅初步总结了翡翠皮壳矿物组成与其内部玉石质量的关系。

Preliminary Study on Components of Crust of Jadeite Jade and Its Relationship with Interior Jade Quality

After a great deal of observation on jadeite jade rough in Pingzhou and Huadu, Guangdong Province, the jadeite jade samples with yellow, white and grayish black crusts are chosen as the major objects for study. Based on naked-eye and microscopic observation, X ray diffraction and EPMA tests, the mineral components and chemical compositions of the crusts with different colours are studied. The results show that jadeite is the main mineral component, but the various secondary mineral components are detected in all the studied crusts. Kaolinite, gibbsite, pyrolusite and hematite are found in the yellow crusts, kaolinite and hydrogrossular in the white crusts, and kaolinite and chlorite minerals in the black crusts. Compared with the interior jade, the contents of the main chemical compositions such as Na20 and SiO2 are relatively lower but CaO, MgO and Fe are enriched in all the studied crusts. In the jadeite jade with yellow crusts, the higher Fe content in its interior jade, the darker the colour of the crust. The chemical compositions of the crust, which are subjects to the forming environment, are difficult to be used in predicting the interior jade quality. The relationship between the mineral component of the crust and its interior jade quality is summarized in the paper.