Study On Gemological Characteristics Of White To Cyan Nephrite Series

White to cyan series of nephrite refers to white,blue-white,cyan,dark blue to black blue.The chemical composition of white to cyan series of nephrite is analyzed in this paper.It is concluded that the main chromatic element of cyan series nephrite-iron.Through the basic properties of gemology,electron probe,x-ray powder diffraction,infrared spectroscopy,laser raman spectroscopy,polarizing microscope,scanning electron microscope,etc,methods.The physical properties,chemical composition,internal structure and spectral characteristics of white to black blue were systematically compared and analyzed.The refractive index of white to cyan nephrite varies greatly as a whole.The refractive index of white to dark blue nephrite ranges from 1.600 to 1.616,and the refractive index of black blue nephrite is 1.644.Ultraviolet-visible spectroscopy analysis showed that all nephrite had absorption bands near 450nm and 650nm.With the deepening of color,the absorption valley of nephrite increased.The relative density of white to cyan nephrite increases gradually with the increase of Fe element.The relative density of white to dark blue nephrite ranges from 2.904 to 3.074.The relative density of the black blue is 3.126.The average vickers hardness of white to dark blue nephrite is 695 to 784 kgf/mm²,and the black blue nephrite is 822kgf/mm².All has glass luster to greasy lusteras a whole.Electron probe analysis showed that with the deepening of color,the main constituent minerals of nephrite is excessive from tremolite to actinolite and iron-actinolite,the main constituent minerals of white nephrite to cyanite were tremolite,the main constituent mineral of dark cyanite was excessive from tremolite to actinolite,and the main constituent mineral of black cyanite was excessive from actinolite to iron-actinolite;X-ray powder diffraction analysis showed that with the increase of color,the cell parameters of nephrite series have a slightly larger trend;Scanning electron microscopy shows that nephrite has higher toughness due to its typical felt-like micro-interweaving structure and stepped fracture.Infrared spectrum analysis showed that the infrared spectrum peaks of nephrite gradually shifted to low wave number with the deepening of the color of the nephrite,and all of them have the absorption peaks of 3672cm^-1.In addition,with the deepening of the color,the absorption peaks of 3660cm^-1,3641cm^-1appeared in the dark-blue nephrite,and the absorption peaks of 3660cm^-1,3644cm^-11 and 3624cm^-1appeared in the black-blue nephrite.Raman spectrum analysis shows that the raman spectrum of black-blue nephrite shifts to low wave number as a whole,especially in the M-OH stretching vibration region,which contains about 3674cm^-1 peaks,compared with white to dark-blue nephrite peaks.In addition,with the deepening of color,the spectrum peaks of 3661cm^-1 appear in cyan nephrite,3661cm^-1 and 3644cm^-1 in dark-blue nephrite,and 3660cm^-1 and 3644cm^-1 and 3624cm^-1 in black-blue nephrite.This main absorption peaks in the vibration zone have great significance in characterizing the chemical composition and color grading of nephrite,the peak intensity ratio method of3674cm^-1,3660cm^-1 and 3641cm^-1 is used to calculate the ratio of Mg²⁺/(Mg²⁺+Fe²⁺)and the relative content of Fe.