The Study On Gemological And Mineralogical Characteristics And Genesis Of Nephrite In Tieli, Heilongjiang

Content: In this paper, we study on the gemology, mineralogy and genesis of nephritedeposit in Tieli, Heilongjiang province, compared the nephrite’s characteristics withthose of which we have known the origin, we aim to find out the differences of origin,mineralogy and quality, and to provide the evidence for identification, developmentand utilization of the nephrite.The color of nephrite from Tieli, Heilongjiang province is mainly light green-white,the color is evenly distributed, part of some samples is light green rarely. The differentsamples’ texture has a bit of differences, most of them are fine, but some are coarse.Their transparency is poor, i.e. slightly transparent to opaque. RI. is in the range of1.60to1.63, the specific gravity is in the range of2.94to2.97, and the Mohshardness is range from5.15to6.79.By IR, Raman spectroscopy, EMPA, EDX, LA-ICP-MS, XRD, it turns out that themain mineral compositions of nephrite from Tieli, Heilongjiang province is tremolite,occasionally calcite particles can be observed. REE mass fraction of nephrite sampleis generally low, LREE and HREE are classified significantly, i.e. that LREE isenrichment and HREE is flat, δEu shows positive and negative anomaly, CeAispositive anomaly. REE pattern curve has a various of types and large changes, itshows that ore-forming fluids are multiple sources and multi-stage superimposedmineralization, and the mineralization environment is oxidative.By observing the sample sheet under polarizing microscope and SEM, the nephritefrom Tieli, Heilongjiang province shows microstructure as felt-like blastic structureand microscopic fibroblastic structure, most diameters of the fibers are less than5μm,some are5to10μm, part of the fibers are semi-orientation to orientation.By EMPA, EDX, combining BSE images observation, we can find out that the surrounding rock of nephrite from Tieli, Heilongjiang province is mainly composed ofdiopside, serpentine, apatite, feldspar and calcite, chlorite, sphene, dolomite andquartz also can be observed. We can infer that there’s two phases of geologicalprocesses coexisting in this region: frist, granodiorite trust into dolomitic marbleleading to contact metasomatism, and make marbles turn to tremolite and diopside;second, thermal fluid containing Si trust into dolomitic marble causing hydrothermalmetasomatism occurred, and make marble serpentinized.Contrasting the nephrite from other deposits, the gemological properties, compositionand structure of nephrite from Tieli, Heilongjiang province is closer to the others, theycan be distinguished by their gemological characteristics and mineral composition.The nephrite from Tieli, Heilongjiang province has white color, fine texture, shows acertain commercial value, it still needs the further study to better develop and utilize.