Gemological Study Of Tremolite Jade In Xianghualing Area,Hunan Province

In this paper we focus on the tremolite jade from Xianghualing area of Hunan Province,systematically study the gemology,mineralogy and petrology characteristics with infrared spectrum,Raman spectrum,electron probe,ICP-MS and X-ray powder diffraction method.To have an comprehensive summary with the mineral composition,structure,spectral characteristics and geochemical characteristics of the tremolite jade from Xianghualing area of Hunan Province.In the study area,tremolite jade is mostly gray-green,with scattered black patches,mostly translucent-slightly transparent,with a greasy luster after polishing.The refractive index is about 1.61-1.62(dot measurement),relative density is 2.935-3.195,and hardness is6-7,The main mineral is tremolite,but it shows a trend of transition to actinolite;the secondary minerals are diopside,talc,pyrrhotite,orthopyroxene,calcite,cassiterite,etc.Under the polarizing microscope,the tremolite particles in the samples are small,generally less than 200 nm,with the content up to more than 90%.Most of the samples are closely interwoven in the form of fibers,showing felt-like cryptocrystalline texture,microfiber-crystal texture and microradial structure.The spectral analysis shows that the b₀ axis of tremolite mineral structure is larger than that of standard tremolite,and the M2 position of tremolite mineral is mostly occupied by Fe²⁺,which is the main reason for the overall green of the sample;the M1 and M3 positions are mostly occupied by Mg²⁺,indicating that the tremolite mineralization temperature in this area is high.The iron content is generally high.,It is found that most of the Fe ions in the samples are in the form of Fe²⁺by estimating Fe²⁺and Fe³⁺in the samples,indicating that the ore-forming environment is in a reduction environment.Inductively coupled plasma mass spectrometry(icp-ms)according to europium anomalies calculated value(?Eu)=0.515 to 0.555 for moderate negative anomaly.The calculated value of cerium anomaly(?Ce)=1.042-1.106 showed almost no anomaly,indicating that the metallogenic environment was reductive.However,the heavy rare earth elements are relatively enriched,while the light rare earth elements are in serious loss.The distribution model of rare earth elements presents a left-leaning trend,which is different from that of other producing areas,and can be used as one of the criteria for identifying the origin.Comparing the tremolite jade from different producing areas,it can be found that the sample is similar to that from other producing areas.Some minor minerals,such as orthorhombic arsenopyrite and cassiterite,can be used as identification characteristics for distinguishing from other producing areas.The structure and mineral assemblage of jade are the main factors affecting the quality of jade.