“油青种”翡翠的矿物学特征及颜色成因

采用X射线衍射、红外吸收光谱及扫描电镜等现代测试方法，对“油青种”翡翠的矿物学特征及颜色成因进行了深入研究。X射线衍射分析结果显示，“油青种”翡翠“肉”的矿物组成为较纯的硬玉，而“皮”由硬玉、绿泥石及纤蛇纹石等三种矿物组成。红外吸收光谱分析所揭示的矿物组成与X射线衍射较为一致，同时发现“油青种”翡翠“肉”及“皮”具有~2 956，~2 919和~2 850 cm-1等三个典型有机质的特征吸收峰。“油青种”翡翠“肉”中硬玉呈现明显的柱状，结晶程度明显好于“皮”中的硬玉，但“皮”中硬玉比“肉”中硬玉明显富含Mg，说明“皮”中硬玉发生过强烈的水/岩反应。纤蛇纹石仅在“油青种”翡翠的“皮”中出现，晶面呈现明显的弯曲状。在“油青种”翡翠“肉”的裂隙处及“皮”中均发现片状绿泥石的存在，可能为“油青种”翡翠致色的主要原因。形成于还原性水/岩反应的绿泥石，会吸附或者包裹一定量的有机质，导致“油青种”翡翠出现有机质的特征吸收峰。

Mineralogy and Colosation of Oil-Green Jadeite Jade

Mineralogy and coloration of oil-green jadeite jade were investigated using X-Ray diffraction (XRD), Fourier transform infrared absorption spectroscopy (FTIR) and scanning electron microscopy (SEM). XRD results show that “flesh” of oil-green jadeite jade is mainly composed of relatively pure jadeite, whereas the “skin” of which is dominated by jadeite, chlorite and chrysotile. The mineral constituents revealed by FTIR are fairly consistent with XRD. Three typical adsorption peaks of ~2 956, ~2 919 and ~2 850 cm-1 related to organic matters occurred in both “flesh” and “skin” of oil-green jadeite jade. Jadeite in “flesh” exhibits an obvious columnar growth and has a better crystallinity than that of “skin”. However, jadeite in “skin” is richer in magnesium than that of “flesh”, suggesting an intense water-rock reaction of jadeite in “skin”. Chrysotile just occurs in “skin” of oil-green jadeite jade, and it presents a curved crystal plane. Flaky chlorite was detected in both cracks of “flesh” and “skin”, which might be the main cause of coloration of oil-green jadeite jade. Chlorite, formed in the reducing water-rock reaction, would adsorb or wrap a certain amount of organic matters, resulting in the occurrence of the characteristic adsorptions of oil-green jadeite jade.