| In this paper,a detailed field geological survey was carried out in the area,and the previous research results were combined according to the actual situation,through conventional gemological test,gemstone microscopic observation,rock flake microscopic observation,infrared spectrum,ultraviolet visible spectrum,Raman spectrum,X-ray powder diffraction,X-ray fluorescence spectroscopy,LA-ICP-MS,electron probe,scanning electron microscopy and other modern test methods to analyze and explore gemological characteristics,mineral composition characteristics and color mechanism of quartzite jade in Hubei Macheng.Studies have shown that the quartzite jade in Hubei Macheng is rich in color and colorless when pure.When it contains iron minerals,it can be yellow,red,green and other colors.The refractive index is 1.53 or 1.54(point measurement),and the relative density is mostly between 2.60 and 2.64.The loss of adsorbed water inside the quartzite jade will cause the“whitening phenomenon”.Quartzite jade has high thermal stability.When the temperature rises,it will cause color change,but when the temperature exceeds 573 degrees Celsius,the low temperature quartz will change to high temperature quartz.The quartzite jade grade is divided into two grades of original stone and finished product,and the finished product is evaluated for quality according to eight factors such as color,gloss,transparency,clarity,special color pattern,texture,blockiness and processingcraft.The main mineral of the quartzite jade is quartz,and its quartz content is above 90%,and it is a granular crystal structure under the microscope.The structure of jade is generally a block structure,a strip structure and a breccia structure.Secondary minerals are mainly goethite,potassium feldspar,goyazite,anatase,mica and kaolinite.According to the microscopic observation,the secondary mineral is more dispersed in the crack between the quartz particles.From the infrared reflectance spectrum,it can be seen that jade is mainly composed of?-quartz,and all samples are obviously split at 778cm-1,instead of weak shoulders,indicating that the quartz-like jade in Macheng,Hubei is closer to quartzite jade.According to the infrared transmission spectrum,the jadeite showed absorption peaks of 3429cm-1and1627cm-1,indicating that the jadestone contained a small amount of adsorbed water.X-ray powder crystal diffraction shows that its main mineral component is quartz,containing a small amount of kaolinite and muscovite.Raman spectroscopy shows that the chromogenic minerals of quartzite jade are hematite and goethite.According to X-ray fluorescence spectrum,the color element of quartzite jade is Fe,which has a decisive influence on the color of jade.From the analysis of trace elements,it can be seen that the content of the five coloring elements Cu,V,Cr,Co,and Ni in quartzite jade is relatively large,and their content has a certain relationship with the color of jade.Analysis of the mineral composition of"dendrite"showed that its material composition was permanganite,organic matter and iron minerals.Goyazite is found in quartzite jade in this paper.Phosphoaluminite is produced in layered or lenticular form,and it changes into siliceous rock along the trend.Based on this,it can be speculated that the goyazite in the Macheng quartzite jade is the residual product of the transition from the phosphor aluminolite to the quartzite.The kaolinite in the Quartzite jade in Macheng,Hubei is mostly point-like and scattered,with feldspar artifacts,and there are many plate-like sericite particles around it,which is presumably caused by kaolinization of granitic surrounding rocks.Kaolinite has good adsorptive ability,and can locally enrich certain coloring components in quartzite jade. |
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