Chemical Composition and Spectrum Characteristic of Nephrite from Luodian, Guizhou Province and Dahua, Guangxi Province

The nephrites from Guangu County, Guizhou Province and Yantan Town of Dahua County, Guangxi Province were selected as the research objects. The chemical composition and vibrational spectra of the samples were analyzed by X-ray fluorescence spectrometer, Fourier transform infrared spectrometer and laser Raman spectrometer. The test results show that the main mineral component of nephrites from Guizhou and Guangxi is tremolite, with a small amount of dolomite. The FeO_T average mass fraction of Guizhou nephrites is 0.268%, which is lower than 1.757% that in Guangxi nephrites, and the FeO_T mass fraction of white nephrites, green white nephrites and green nephrites increase in turn.With the enhancement of the isomorphism of Fe²⁺ to Mg²⁺ in the crystal structure, the degree of M-OH vibration band splitting in the infrared and Raman spectra of nephrite is gradually increased. The highest degree of division comes from green nephrite of Guangxi. The middle infrared absorption bands around 3 674, 3 660, 3 644 cm^-1 are caused by the fundamental frequency vibration of OH(Mg, Mg, Mg), OH(Mg, Mg, Fe ²⁺) and OH(Mg, Fe²⁺, Fe ²⁺), and the near-infrared absorption bands around 7 182 cm^-1and 7 154 cm^-1 are caused by the double frequency vibration of OH(Mg, Mg, Mg) and OH(Mg, Mg, Fe ²⁺). The Raman peaks around 3 672, 3 658, 3 642 cm^-1 are caused by M-OH stretching vibration. Since the overall Fe mass fraction of Guizhou nephrites is lower than that of Guangxi nephrites, there is no splitting phenomenon in the relevant peaks.