Gemological Characteristics And Analysis Of Mineralization Of Cyan Nephrite In Xinjiang

Since ancient times,Chinese people are fond of jades while jades are also one of the origins of Chinese culture.Because nephrites contain many values,researching them is deemed to a significant piece of work for a long time.Although there are many researches about nephrite,most of them are related to culture,petrological and gemological characteristics.There are only a few studies in nephrite deposits.This research is based on investigation of market,gathering four types of samples from two origin places,including Jumo cyan nephrite which contains cyan,caramel,and blackest colors,black cyan nephrite from Taxkorgan,cyan nephrite from Qinghai,and a representative artificial nephrite called emulsification glass from Xinjiang.Also,I have done field research and systematically collected samples,analyzing mineralization.By means of slicing up,observing under telescope,EPMA,IR,XRF,and ICP,we analysis samples we have collected to analyze mineral composition and texture of nephrites' inside.Through researching of gemological and petrological characteristics of cyan nephrite,this research focuses on discussion of lithological characteristics and mineralization,aiming to elaborate some problems about coloring elements,characteristics of counterfeit identification,genesis of mineral deposit,metallogenic model,and many other issues.The nephrite metallogenic belt covers study area,and this region has found many mineral occurrences of nephrite.In this region,there are many fractures accompanied by shear characteristic.Also,magmatite activities are frequent.The lithology of visible stratas in study area is mainly dolomite marble.There are many fractures in the study area,and magmatite activities are frequent,too.We have found five bedding ore bodies with small scale,and they are mainly stratiform-like and lentoid.In addition,they are variegated.Tremolite content of cyan nephrite is 95% or so,and we also are able to see some accessory minerals,including apatite,phlogopite,and so forth.It is usually to see crystalloblastic texture with cryptocrystalline felt shape.The reason why viscosity of nephrite is largest in Jade is that mineral particles are very fine while they also combine together with each other.According to research results of IR,the strongest absorption belt may be seen between 1150-850cm-1 and absorption peak may be seen between 980 and 1000cm-1.Study of macroelement shows content of oxide of nephrite of each area is relatively stable.As for microelement,some elements in different nephrite may not same.For example,from white nephrite to cyan nephrite,content of FeO gradually increases.Besides,some researchers study REE and find that there are some differences among different colors.As to isotopic studies,we believe hydrothermal solutions are not single.The research area mainly exposes marble.According to investigation of studying Ca/Mg in wall rock,they believe wall rock of Xinjiang nephrite deposit which usually is marble is rich in magnesian while wall rock of Qinghai which usually is dolomite(marble may be seen)is rich in calcium.There are two genesises of nephrite deposit.The first one is jasper deposit.It is related to ultrabasic rock.Some scholars consider the cause of formation of this deposit is alteration factor of ultrabasic rock.The second one is contact metasomatism factor which are formation of nephrite deposit of other colors.Additionally,cause of nephrite deposit likes skarn deposit,seeing in contact zone of intermediate-acid intrusive and carbonatite,possessing multi-stages.Through comparison,we find that there are some minerogenetic condition differences between east and west of Kunlun,including wall rock,metallogenic fluid,and many other factors.At last,according to documents and the characteristics of mineralization in study area,we divide ore-controlling factors into three points,intrusive rock,lithology,and structure.The intrusive rock usually is intermediate-acid magma.The lithology of wall rock is mainly marble(sometimes dolomite can be seen in some area).As to fracture,ore body is often seen in the second level of deep fracture.