Gemology Study Of Nephrite (Hetian Yu) From Xinjiang

Nephrite (Hetian Yu) is the most famous jade in China, with long historical and cultural backgrounds. The thesis performs the gemological investigation for the Hetian Yu from Xinjiang province, which focuses on the Omixia primary deposit and Yurungkash river secondary deposit. This study helps to understand the relationship between the quality and the micro-texture of Hetian Yu, as well as to solve some technical challenging for the identification of Hetian Yu.The investigation work include geological field survey for the primary deposits (shanliao) and the secondary deposits; as well as the major trade markets for the Hetian Yu; shanliao( primary deposit), pojixing Hetian Yu, bingqixing Hetian Yu, shanliushui liao, ziliao and gobi liao have been collected. In the laboratory, we performed Microscope observation, Electron microprobe analysis, Fourier infrared spectroscopic analysis, Raman spectral analysis, Ultraviolet-visible absorption spectral analysis, X-ray fluorescence spectrometry analysis and X-ray power diffraction analysis, etc. for collecting and analyzing gemological properties and the characteristics of Hetian Yu from Xinjiang province.It was found that the main component of Hetian Yu is tremolite, the secondary minerals are diopside, apatite, chlorite and sphene, etc. The tremolite in Hetian Yu appears as the felt-like texture, fibrous texture and radial structure. In the Omixia deposit, the microcrystal of tremolites display relatively larger size in grains, distributed with good orientation arrangement, resulting in the obvious hierarchical structure, rough texture and easily broken.“Shuixian”can be found in the ziliao from Xinjiang Hotan region, which consist of“shuixian”is tremolite. The tremolites in“shuixian”arrange paralleled with fibrous structure, the change of the micro-texture from the main body of the jade to“shuixian”is very clear. The surface coloration observes on the Omixia samples is the secondary coloration, spectroscopic studies demonstrated that the basic component materials for the colorations are similar, which consist of iron containing minerals. The skin coloration on the surfaces of ziliao is formed by the geological processes during the formation of ziliao, the geochemical conditions, such as iron content, the level of the groundwater and the pH of water, etc. control the coloration. We also found that the ziliao’s main characteristics are macro-morphology, fracture characteristics, the surface of skin color and surface micro-characteristics etc.Spectroscopic studies show that the samples of Hetian Yu with same color but from different deposits have the similar characteristics of spectrum, various color has various characteristics. These findings could help us to solve some technical challenging for the identification of Hetian Yu.