新疆紫色直闪石玉的宝石学特征及颜色成因探讨

Gemmological Characteristic and Colour Origin of Purple Anthophyllite Jade from Xinjiang, China

  • 摘要: 本文研究一种新疆软玉市场出现的外观质地与软玉相似的紫色直闪石玉,其产量稀少,价格较高。常规宝石测试其折射率为1.61(点测),相对密度为3.00,紫外灯下荧光为惰性。通过X射线粉末衍射仪、傅里叶变换红外光谱仪、偏光显微镜、拉曼光谱仪测试结果综合分析表明,该样品的主要矿物组成为直闪石、呈纤维状分布,紫色部分含有少量的斜绿泥石、而粉色部分不含绿泥石。通过显微紫外-可见光谱仪、能量型色散X射线荧光能谱仪及扫描电子显微镜和能谱仪测试结果综合分析表明,直闪石玉样品中粉色部分颜色成因为含Fe,Mn的直闪石造成,而紫色部分颜色成因为含Fe, Mn的直闪石及含Cr的斜绿泥石共同作用形成,样品紫色颜色深浅与斜绿泥石含量呈现正相关。

     

    Abstract: A kind of rare and high price purple anthophyllite jade which is similar to nephrite in appearance and texture found in Xinjiang nephrite market was studied. According to conventional gemmological tests, the refractive index of the purple anthophyllite jade is 1.61 (point measurement), the relative density is 3.00, and the fluorescence response under UV lamp is inert. The comprehensive analysis of X-ray powder diffractometer, Fourier transform infrared spectroscopy, polarizied microscope and Raman spectroscopy tests showed that the main mineral component of the anthophyllite jade sample is anthophyllite with fibrous distribution. The purple part of the sample contains a small amount of clinochlore, while the pink part does not contain clinochlore. Further comprehensive analysis by micro-UV-Vis spectrometer, energy dispersive X-ray fluorescence spectrometer, SEM scanning electron microscope and EDS spectrometer showed that the colour of the pink part of the anthophyllite jade sample is caused by the anthophyllite containing Fe and Mn elements, while the colour of the purple part is caused by the combined action of the amphibolite containing Fe and Mn elements and the clinochlore containing Cr element. There is a positive correlation between the saturation of purple colour and the content of clinochlore.

     

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