Study On Gemmological And Mineralogical Characteristic Of Guilin Chicken Blood Jade From Longsheng,Guangxi Province

The essay based on the previous studies,through the field investigation and sample collection,with the help of conventional gemological equipment,optical microscope,X-ray powder diffraction spectrometer,electron probe,microscopic Raman spectrometer,infrared spectrometer,UV-visible-near infrared spectrometer and other equipments,to make a systematic research on gemological and mineralogical characteristic and the mechanism of coloration of Guilin chicken blood jade?GCBJ?,to discuss the genesis of ore deposit.GCBJ has red,black,yellow,green,purple and other colors,has the poor transparency.Most of it are glass luster,refractive index of 1.53 or 1.54,no absorption spectrum and luminescence phenomenon.The relative density have a larger variety,with a minimum of2.61 and a maximum of 3.39.The most of GCBJ are crystalloblastic texture,massive structure.The major constituent mineral of GCBJ is quartz.The range of granularity of quartz varies greatly.Most of quartz exist in the form of allotriomorphic granular.In addition to the main mineral quartz,there are also the minor minerals such as hematite,magnetite,goethite,talc,dolomite,chlorite and so on.The same color series of GCBJ in the secondary mineral content and its distribution characteristics are different:in the red series of GCBJ,some only contain hematite,some contain talc and extremely small amount of chlorite besides hematite;in the“red blood and black ground”series of GCBJ,some contain magnetite besides hematite;in the purple series of GCBJ only detect the existence of quartz,there are no other minerals;in the green series of GCBJ found that the existence of dolomite besides chlorite.There are many different states of iron oxide and hydroxide in GCBJ,such as hematite,maghemite,magnetite,goethite,fibrous ore and cubic iron and a variety of different states.Among of them,hematite is common in GCBJ,the presence of magnetite will deepen the black tone,in the yellow series of GCBJ the content of goethite is higher than others.The color genesis of red,yellow and black of GCBJ are related to the content and the state of existence of hematite:The more concentrated the distribution of hematite,the deeper the color of the corresponding GCBJ.Scaly hematite make the color of GCBJ deeper,disseminated hematite make GCBJ in yellow.When the density and distribution of hematite is appropriate,GCBJ will present colors such as red,orange-red,orange and so on.When the content of magnetite is more than other secondary mineral will make the GCBJ appears deep black;when the existence of chlorite will make the GCBJ appears green;when the presence of talc and dolomite will reduce the hardness of GCBJ,the presence of talc will increase the transparency of GCBJ,and the presence of dolomite will reduce the transparency of GCBJ.Fe³⁺instead of Si⁴⁺to form a hole color center will make the GCBJ appears purple.Through the study of the petrographic characteristics,the distribution of minerals and so on of GCBJ,and combined with the study on the geology of Guilin Longsheng area and the research on the GCBJ by our predecessors regard as:after Sipu orogeny,the mantle plume upwelling makes Rodinia super-continental pyrolysis,rift basin group of south China formed in the area of Guilin Longsheng,and the occurrence of submarine volcanic sedimentation.Because of submarine volcanic sedimentation makes the temperature rise of sea water in the region,greatly enhance the dissolved of seawater on the siliceous compounds and iron compounds.After the sea water is cooled,the siliceous compounds and the iron compounds will precipitate to form the original siliceous rocks.In the Caledonian motion,the magmatic rock carrying the lower minerals of the siliceous rocks enter the siliceous rocks,and the magmatic hydrothermal fluids cause the recrystallization of the siliceous rocks to form quartzite.Then the quartzite has experienced the tectonic activities such as the Indosinian movement and the Xuefeng orogeny.Eventually formed GCBJ.