昌化黄石的宝石学和矿物学特征研究

Gemmological and Mineralogical Characteristics of Changhua Yellow Stone

  • 摘要: 昌化黄石是产于浙江昌化,外观上与田黄非常相似的一种图章石,市场上称为“昌化田黄”,对其宝石学和矿物学特征进行研究有利于对田黄进行科学鉴定,尤其是对产地鉴定具有重要意义。运用显微镜及偏光显微镜、X射线粉末衍射仪、红外吸收光谱仪和扫描电子显微镜等仪器测试方法对昌化黄石样品石皮的显微特征,主、次要矿物组成和表面及断口微形貌特征等进行了研究,并与其石肉的X射线粉末衍射图谱、红外光谱特征进行比较。结果表明,大部分昌化黄石石皮的主要矿物组成为有序度低的地开石-高岭石混合矿物,个别由有序程度较低的纯地开石组成,石肉与石皮的矿物种类一致,但高岭石含量更高, 有序度度差距不大。昌化黄石表面的白色凹坑内包含次要矿物:赤铁矿、硫磷铝锶石、石英、白云石和石膏等。石皮的微形貌特征研究表明, 组成石皮的高岭石族矿物颗粒直径约为5 μm,地开石颗粒之间间隙不清晰,颗粒边界圆滑,集合体呈书本状叠置排列,而新鲜断面的结晶程度良好,呈假六方片状或叠瓦状堆叠。

     

    Abstract: Changhua yellow stone is produced in Changhua, Zhejiang Province. Its appearance is very similar to Tianhuang, and the gemmological and mineralogical study of Changhua yellow stone is of great significance to identify Tianhuang, especially its origin scientifically. In this paper the authors used microscope and polarizing microscope, X-ray powder diffractometer (XRD), infrared absorption spectrometer (FTIR) and scanning electron microscope (SEM) to study the microscopic characteristics, primary and secondary mineral components, and the fracture micro appearance characteristics of the rough stone crust and compared with the stone's internal XRD and FTIR characteristics. The results showed that the external mineral components of most Changhua yellow stones are mixed minerals of dickite and kaolinite in a low degree of order, and several samples are composed of pure dickite of lower degree order. Meanwhile, the internal mineral components of the stones are similar to the external, nevertheless, the content of kaolinite is higher, and there is little difference in the degree of order. The chemical composition of the main constituent minerals of the external and interior of Changhua yellow stone can be obtained by quantitative analysis of energy spectrum. There are many kinds of secondary minerals that are mostly distributed in the white pits on the crust of the Changhua yellow stone, including hematite, svanbergite, quartz, dolomite and gypsum etc. The distribution morphology was observed by EDS energy spectrum test.For the micro appearance characteristics, the diameter of kaolinite mineral particles constituting the crust of the stone is about 5 μm, and the gap between dickite particles is unclear. The particle boundary is smooth, and the aggregates are arranged in book shape, while the crystallization degree of the internal of the stone is good, which is stacked in pseudo-hexagonal sheet or imbricate shape.

     

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