一种南非蛇纹石玉的宝石学特征及其颜色成因

Gemmological Characteristic and Cause of Colour of Serpentine from South Africa

  • 摘要: 采用常规宝石学测试,X射线粉末衍射仪(XRD)、红外光谱仪、偏光显微镜、电子探针及紫外-可见分光光度计(UV-Vis)等现代测试方法对市场上新出现的南非蛇纹石玉的矿物组成、结构特征、化学成分及颜色成因进行了研究,并与辽宁岫玉做了对比。X射线粉末衍射的分析结果表明,南非蛇纹石玉的主要矿物组成为叶蛇纹石,次要矿物组成为利蛇纹石、绿泥石,与辽宁岫玉的组成类似;电子探针定量的分析结果显示,南非蛇纹石玉的主要化学成分为Mg,Si,Fe,Al,Mn等;UV-Vis结合电子探针分析结果显示,南非蛇纹石玉的主要致色元素为Fe。Fe3+的d-d电子跃迁能够导致南非蛇纹石玉样品带有浅黄色调,而Fe2+→Fe3+电荷转移跃迁作用决定了南非蛇纹石玉呈现绿色。

     

    Abstract: The serpentines reported from South Africa were found in the jewelry market recently. Mineral components, structural characteristics, chemical compositions and the cause of colour of the serpentine samples from South Africa were investigated with the help of X-ray powder diffraction spectrometer (XRD), infrared spectrometer (FTIR), polarizing microscope, electron microprobe (EPMA) and ultraviolet-visible spectrophotometer (UV-Vis). In addition, mineral components of serpentine from South Africa were compared with the serpentine from Liaoning Province, China.The results show the main mineral components of serpentine from South Africa were antigorite with a small amount Of lizardite and chlorite。which is similar to the serpentine from Liaoning Province.The result of electron microprobe demonstrates that the main chemical compositions of the serpentine sample are Si,Mg.It also contains a small quantity of A1 and trace amount of Fe,Mn and SO forth.The results of UV Vis combining with EPMA show that the coloration might result from the chemical element Fe.The d-d electrons transition of Fe3+ causes the pale yellow colour,and the charge transfer of Fe2+→Fe3+ is the major reason for the green coloration of serpentine from South Africa.

     

/

返回文章
返回