The Study On Gemological Characteristics And Genesis Of Mixian Couty Jade From Henan

There is a quartz jade produced in Xinmi city,Henan Province,called Miyu(Mixian County jade).It's smooth and colorful,including red,yellow,purple,black,etc.The Miyu has a reputation of “Henan cui” in that its' green is as gorgeous as jadeite.The paper on the basis of spot investigation briefs the geological environment of Xinmi city and the occurrence of mining area,analyzes the factors of form conditions,and summaries the gemological characteristics by doing some tests.Large-scale equipment like electron microscope,Raman spectrum,X fluorescence spectrum and X ray diffraction is used to study the color genesis and texture formation systematically.gaining the data of mineral composition and discussing the color mechanism,the paper provide a theoretical basis for exploiting Miyu resourses.The Miyu which is in vein and lenticular state distributes discontinuously in Zhu Quan Temple mining.The ore body is quartzite,and the strata is stable and has a lamellar structure.Due to folds in the area,crack developed,and the green kind fill in.Most Miyu are white and green,other color like red,yellow,purple and black mingles.Miyu has a glassy luster or greasy luster,translucent to transparent.The refractive index is 1.54.The relative density is 2.631 ~2.658.Ultraviolet florescence is inert.And unlike the other,the green kind shows dark red in CCF.Converting the microhardness into Mohs hardness,Miyu's Mohs hardness is from 6.4 to 6.9.Miyu are granoblastic texture and fine grained texture,massive structure.The average content of main chemical components was SiO2=98.13%,followed by Al2O3=0.67%,Fe2O3=0.24%,K2O=0.18%,CaO=0.16%,MgO=0.06%,Na2 O,TiO2 trace.The main components of different color are essentially the same,with the color change minor chemical composition are different.The green kind has high Cr content,and Fe content in yellow,red,purple,black is high.With polarized optical microscope,electron microprobe,X ray diffraction,Raman spectroscopy,the conclusion is that quartz is the main mineral of Miyu,content above 97%,and the minor minerals are sericite,zircon,tourmaline,iron minerals etc.The green sericite in green Miyu either fill in the cracks between quartz or are located over quartz.The yellow goethite spheres distributing along the quartz gap cause the yellow color.And red and black Miyu have hematite slices,showing red when the slices are thin,black when thick.The hematite also exists in purple Miyu,and is possibly related to its color genesis.