Study Of Gemological Mineralogy Of Green Nephrite From Pakistan

Green nephrite is loved by people as one of the important varieties of nephrite.The main producing area of Pakistan nephrite is in the northwestern part of Pakistan and the border area of Afghanistan.The rocks in the study area are mainly Neoproterozoic to Mesozoic rocks,which are magnesia-ultramafic ophiolite complexes,and their genesis are ultrabasic rocks.Pakistani nephrite as a new production variety in the market in recent years,the market acceptance is not high.Previous studies on Pakistan nephrite have been less,and the main research is on the color characteristics of jade and the texture characteristics of jade.The specific mining area is not clear,and the gemological characteristics of Pakistan nephrite are not comprehensively analyzed.This paper takes the nephrite produced in Pakistan as the research object,and uses the modern testing techniques such as electron probe,X-ray powder diffraction analysis,infrared spectroscopy and Raman spectroscopy to carry out a more comprehensive mineralogical and gemological characteristics of Pakistan nephrite.The color of the Pakistani nephrite was analyzed by UV-Vis spectrometer and LA-ICP-MS.The results show that Pakistan nephrite is mainly composed of a series of minerals of the tremolite-positive symmetry.Among them,under the polarizing microscope,the main components of Pakistan nephrite are tremolite and actinolite,and the impurity minerals are chromite and chlorite.For a typical fiber interweaving structure,the structure is mainly a block structure.The results of electron probe analysis indicated that the main mineral component of Pakistan nephrite was tremolite.With the increase of iron content,the tremolite minerals transitioned to the erectite minerals.The secondary minerals were chromite,chlorite and magnetite.X-ray powder diffraction results show that the parameters of Pakistan nephrite are consistent with the standard tremolite absorption peaks.Scanning electron microscopy showed that the nephrite sample was a felt-like crystal structure,because its felt-like structure made nephrite strong and hardest to break and break.The infrared spectrum and Raman spectrum of the sample were analyzed,and the attribution of the vibrational spectrum was discussed.According to the analysis of the color of Pakistan,the results of ultraviolet-visible spectrometer show that the main reflection peaks of the reflection spectrum of nephrite are concentrated at 400-520 nm.The main wavelength of the nephrite sample is between 481.63 nm and 492.21 nm.That is,the wavelength isbetween cyan and green,and the color of the sample is a mixed color of green and cyan in different proportions.The LA-ICP-MS experiment found that the Cr and Ni elements are the main elements determining the depth of the green nephrite in Pakistan.Fe can make the green dark to grayish green and brownish green,the content of Cr,Ni and Fe decreased obviously with the color lightening.