The Gemological Characteristic And Cause Study Ofnephrite In Nachitai Golmud Qinghai China

Nephrite jade, the representative of Chinese jade culture, is favored by people with its gentle luster and soft texture. The gradually depleting source of nephrite jade in Hetian results in high price of nephrite, increasing number of varieties imitationsas well as multi-means of making counterfeits. In recent years, a new nephrite deposit was found in east Kunlun area in Qinghai. Detail study of nephrite deposits characteristics in Qinghai provide an opportunity to relieve current problems above.We carry out studieson the Nachitai nephrite orefield in Qinghai, Golmud.The orefield is located in the east Kuen-Lun mountain range fault zone.The wall rock for nephrite is carbonate of upper proterozoic Wanbaogou group. The rockwithin the mining area consist of mafic diabase, granodiorite, serpentine, magnesian carbonate, tremolitic marble. We select samples from different rock masses and their boundaries.Methods including hand specimen description, relative density test, slices grinding, microscope observation, RI test,electron microprobe analysis, X-ray powder diffraction and so on were undertaken. By integrating the data and information from these tests, the structure and texture as well as the jadeization of tremolitic marble.The portion containing high-abundance tremolite is white to pale green, with weak oily luster. The RI is 1.61,SG is up to 2.9215. It is reasonable to name it “Nephrite”. Electron microprobe results show that the main minerals are tremolite, calcite, talc in Jadeized part. Tremolite forms include microscopic cryptocrystalline, fiber etc.The wall rock is magnesian marble. Intrusive rocks are consist of Caledonian granodiorite, mafic diabase. The magmatic hydrothermal invasion in the late.Active ion exchange among wall rock, intrusive rocks and the late-staged hydrothermal fluids leads to formation of tremolite accompanying strong tectonic movement.Mafic diabase has been heavily altered. Most pyroxene has completely altered into chlorite, calcite and actinolite.Granodiorite, magnesian carbonate, diabase and late hydrothermal fluid are indispensable in the formation of nephrite.