“金鳞石”(锂云母玉)的宝石学特征

Gemmological Characteristic of “Jinlinshi” (Lepidolite Jade)

  • 摘要: 采用常规宝石学测试,并结合扫描电子显微镜、偏光显微镜、傅里叶红外光谱仪、X射线能谱仪、X射线粉末衍射仪、激光拉曼光谱仪等大型仪器,对市场上出现的一种商业俗称“金鳞石”的宝石材料的宝石学特征、矿物组成、化学成分等进行了测试与分析。结果表明,“金鳞石”样品为锂云母玉,其折射率为1.55(点测),摩氏硬度为2~3,相对密度为2.83;红外光谱和拉曼光谱的测试结果表明样品与云母的图谱基本一致;扫描电子显微镜观察结果显示样品为矿物集合体,具有极完全解理,参差状断口,细粒鳞片变晶结构;X射线能谱结果显示样品主要含有Si、Al、K、F、O等;偏光显微镜、X射线粉末衍射分析结果均表明样品主要由锂云母和少量白云母组成,按照《GB/T 16552—2010 珠宝玉石 名称》相关规定,应定名为锂云母玉。 长波紫外荧光下观察锂云母玉样品内部网格状裂隙内的荧光呈强蓝白色,与锂云母玉样品主体弱紫色荧光颜色不一致,显微镜下观察发现裂隙表面的光泽差异明显,伴有密集的气泡群,表明锂云母玉样品经过充填处理。

     

    Abstract: The gemmological characteristics, mineral components, chemical compositions of “Jinlinshi” called by salers were researched by the conventional gemmological tests, scanning electron microscope (SEM), polarizing microscope, Fourier transform infrared spectrometer (FTIR), X-ray energy spectrometer (EDS), X-ray powder diffraction spectrometer (XRD), laser Raman spectroscopy (Raman), etc. The results showed that the refractive index of “Jinlinshi” sample is 1.55 (point measurement), and Mohs hardness is 2-3, and relative density is 2.83. FTIR and Raman test results agreed with spectrum of mica.The analysis of SEM indicated that the “Jinlinshi” sample is mineral aggregate, which has perfect cleavage, uneven fracture and scale crystalloblastic texture. EDS results showed that the “Jinlinshi” sample is mainly composed of Si, Al, K, F and O, etc. The analysis of polarizing microscope and XRD results showed that the “Jinlinshi” samples are mainly composed of lepidolite and minor muscovite, which are closely contacted and randomly arranged. According to GB/T 16552-2010 Gems─Nomenclature, the “Jinlinshi” sample should be named as “Lepidolite jade”. The interal gridded fracture of “Jinlinshi” sample showed strong blue and white fluorescence under long wave ultraviolet, which is different with the weak violet fluorescence of “Jinlinshi” sample. By microscope, the difference of the surface gloss of fracture was obvious, with the dense bubble group. It can be concluded that the “Jinlinshi” samples were filled.

     

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