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Study On Gemological And Mineralogical Characteristics And Genesis Of Nephrite In Tiantai, Qiemo, Xinjiang

Posted on:2017-01-10Degree:MasterType:Thesis
Country:ChinaCandidate:L J WuFull Text:PDF
GTID:2180330482484141Subject:Materials engineering
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Qiemo, Xinjiang is one of the most important producing areas of nephrite. In this paper, we study on the gemology, mineralogy and genesis on nephrite deposit in Tiantai, Qiemo, Xinjiang, and to provide a theoretical basis for the development and utilization of nephrite resources. Focus on mineralogical characteristics(including microstructure, mineral composition, chemical composition, trace element distribution,etc.), Survey the geological features and genesis of this mine.The following conclusions from this test of conventional gemological identification apparatus: The main color of nephrite from Tiantai, Qiemo is white,pale yellow-brown-dark brown, light green-dark green to bluish-based; transparency is slightly transparent; the Mohs hardness is about 6.29; the specific gravity is about2.96; RI is about 1.60.By the test of polarizing microscope and SEM, conclude that: the nephrite from Tiantai, Qiemo shows microstructure as microscopic fibroblastic structure and felt-like blastic structure. The main structural types are massive structure.By the use of EMPA, IR, XRD, Raman spectroscopy, it turns out that the main mineral compositions of nephrite from Tiantai, Qiemo is tremolite, impurity minerals are diopside, dolomite, sphene, epidote, magnetite, apatite, limonite, etc.Theconclusions of chemical composition from the test: The chemical composition of nephrite from Tiantai, Qiemo is similar with tremolite:Ca2Mg5[Si8O22](OH)2, and the degree of the greenness is determined mainly by iron.In the study of the color-genetic mechanism of brown jade, the test show that the concentration of the brown color has no good relationship with Fe element, samples with deeper color could have lower Fe content. We infer that the brown coloration of nephrite is due to goethite distributed in the tremolite particles or the microcracks.Analyzing the oxygen and silicon isotopic and the rare-earth elements, we conclude that nephrite deposits in Tiantai, Qiemo, Xinjiangare hydrothermal contact metasomatic deposits, which have occurred in the contact between intermediate-acidic intrusive rocks and dolomitic marble.
Keywords/Search Tags:nephrite, Qiemo, mineral composition, chemical composition, genesis
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