西藏丁青象牙玉的玉石学及矿物学特征

Gemmological and Mineralogical Characteristics of Dingqing Ivory-jade in Tibet

摘要: 矿床产于西藏丁青县，其质地温润细腻，色如象牙，故得名“象牙玉”，矿石呈砾石状，部分呈磨圆状、椭圆状。运用紫外可见光谱、X射线荧光光谱、红外光谱、X射线粉晶衍射及扫描电镜等技术对象牙玉进行了玉石学及矿物学特征研究。结果表明：象牙玉摩氏硬度在4~6，相对密度2.92~3.05，折射率1.62~1.70，无多色性，无特征吸收谱带，主要矿物成分为菱镁矿（MgCO₃），少量石英（SiO₂），微量方解石（CaCO₃）。丁青象牙玉的玉石学及矿物学特征可作为产地鉴定的依据。

Abstract: This deposit is located in Dingqing county, Tibet. Its texture is warm and delicate, and its color is like ivory, so it is named "Ivory jade". The ore is gravel-shaped, and some of it is round and oval. The gemmological and mineralogical characteristics of Dingqing Ivory-jade from Tibet are studied by means of UV-Vis Spectroscopy, X-ray Fluorescence Spectroscopy, Infrared Spectroscopy, XRD and SEM. The results show that: the Mohs hardness of Ivory-jade is 4~6, the relative density is 2.92~3.05, the refractive index is 1.62~1.70, no polychromism nor characteristic absorption band, the main mineral composition is magnesite (MgCO₃), with a small amount of quartz (SiO₂), trace calcite (CaCO₃). The gemmological and mineralogical characteristics of Dingqing Ivory-jade can be used as the basis of its origin identification.