新疆“昆仑金玉”的宝石矿物学特征

采用X射线粉末衍射、傅里叶红外吸收光谱、原子吸收光谱、扫描电子显微镜及宝石学常规测试等分析方法,对具有代表性的两种颜色的新疆"昆仑金玉"样品的宝石矿物学特征进行了深入研究。结果表明,"昆仑金玉"的矿物组成为蛇纹石,深绿色品种为叶蛇纹石,黄绿色品种为利蛇纹石,深绿色品种的硬度高于黄绿色品种;"昆仑金玉"的颜色与Fe元素的质量分数密切相关,黄绿色品种中Fe的质量分数高于深绿色品种,其中,不同的Fe~(3+)/Fe~(2+)比值致"昆仑金玉"呈现不同的色调;深绿色品种中的叶蛇纹石和黄绿色品种中的利蛇纹石在扫描电子显微镜下均展现典型的片状外观,深绿色品种中的叶蛇纹石边缘为参差状,而黄绿色品种中的利蛇纹石发育圆化的边缘,这种形态的差异说明两种蛇纹石具有不同的内部结构。红外光谱结果显示,3 644cm~(-1)处"肩状"吸收峰的出现,说明深绿色品种中的叶蛇纹石和黄绿色品种中的利蛇纹石具有不同的内部结构。

Gemmological and Mineralogical Characteristic of Jade from Kunlun,Xinjiang, China

The jades from Kunlun, Xinjiang, with two colours varietis were investigated by using X-ray powder diffraction spectrometer (XRD), Fourier infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), scanning electron microscope (SEM) and conventional gemmological tests for studying the gemmological and mineralogical characteristics.The results showed that the jades from Kunlun are composed of serpentine, and the dark green variety and the yellow green variety are antigorite and lizardite respectively.The dark green variety has a higher hardness than that of the yellow green variety.The colour of jade from Kunlun is closely related to iron content.The dark green variety has a higher iron content than that of the yellow green variety, with different Fe3+/Fe2+ ratio leading to different hues.Both of the dark green variety and the yellow green variety exhibited a flake-like appearance under SEM.The dark green variety has a ragged edge, and the yellow green variety has a rounded edge, which suggest the different interior structure of antigorite and lizardite.The occurrence of a shoulder adsorption at 3 644 cm-1 also suggested different interior structure of antigorite and lizardite.