阿富汗潘杰希尔祖母绿的宝石学特征及颜色成因

Gemological Characteristics and Color Genesis of the Emeralds from Panjshir,Afghanistan

阿富汗祖母绿颜色艳丽,开采历史悠久,矿床主要集中在潘杰希尔山谷中,与该处的断裂带紧密相关。本文通过宝石显微镜、Diamond View^(™)(钻石紫外荧光仪)、紫外-可见分光光度计、能量色散X射线荧光光谱仪(XRF)等仪器对阿富汗潘杰希尔祖母绿的宝石学特征和颜色成因进行了研究。结果表明,阿富汗潘杰希尔祖母绿表面常见黑褐色、银灰色围岩和褐黄色浸染物,内部管状包裹体和锯齿状流体包裹体丰富,可见六方柱状负晶。Cr_(2)O_(3)、V_(2)O_(3)、FeO含量范围分别为0.17~1.36wt.%,0.14〜0.47wt.%,0.19〜2.60wt.%,主要致色离子为Cr^(3+)、V^(3+),铁元素明显影响着绿色的深浅程度,颜色越深,铁的特征吸收越明显。相较尼日利亚、坦桑尼亚和哥伦比亚的祖母绿,阿富汗祖母绿属于Fe含量较低型祖母绿。

Afghan emeralds have bright color and a long history of exploitation.The deposits of Afghan emeralds are mainly concentrated in the Panjshir Valley,which are closely related to the fault zone.In this paper,the gemological and chemical characteristics of Panjshir emeralds in Afghanistan were studied by gemological microscope,Diamond View^(™),UV-Vis spectrophotometer and Energy Dispersive X-Ray Fluorescence Spectrometry(EDXRF).The results show that dark brown and silver gray surrounding rock and brown yellow disseminated matter are common on the exterior of Panjshir emerald in Afghanistan.The tubular and serrated fluid inclusions are abundant in the interior,with visible hexagonal prism shape negative crystals.The content ranges of Cr_(2)O_(3),V_(2)O_(3) and FeO are 0.17〜1.36wt.%,0.14~0.47wt.%,0.19〜2.60wt.%,respectively.The main chromogenic ions are Cr^(3+),Vacations and iron element obviously affects the shade of green.The darker the color is,the more obvious the characteristic absorption of iron element is.Compared with Nigeria,Tanzania and Colombia emeralds,the content of Fe in Afghan emerald is lower.