Gemmological and Mineralogical Characteristic of Jade from Kunlun, Xinjiang, China

The jades from Kunlun, Xinjiang, with two colours varietis were investigated by using X-ray powder diffraction spectrometer (XRD), Fourier infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), scanning electron microscope (SEM) and conventional gemmological tests for studying the gemmological and mineralogical characteristics. The results showed that the jades from Kunlun are composed of serpentine, and the dark green variety and the yellow green variety are antigorite and lizardite respectively. The dark green variety has a higher hardness than that of the yellow green variety. The colour of jade from Kunlun is closely related to iron content. The dark green variety has a higher iron content than that of the yellow green variety, with different Fe³⁺/Fe²⁺ ratio leading to different hues. Both of the dark green variety and the yellow green variety exhibited a flake-like appearance under SEM. The dark green variety has a ragged edge, and the yellow green variety has a rounded edge, which suggest the different interior structure of antigorite and lizardite. The occurrence of a shoulder adsorption at 3 644 cm^-1 also suggested different interior structure of antigorite and lizardite.