The Yurungkax River and Karakax River (White Jade and Black Jade) are two main placer nephrite sites located in Hetian, Xinjiang. They are well known historically for their valuable white, green and black nephrite, respectively, with a long history of use in the world. In this study, electron microprobe (EPMA) analysis was used to study green nephrite samples. The result shows that low Cr and Ni (Cr₂O₃ = 0.00 to 0.06% and NiO = 0.00 to 0.09%, respectively) are constant in these samples, consistent with the content of the marble-type nephrite but different from the content of serpentinite-related nephrite (Cr₂O₃ = 0.07% to 0.43% and NiO=0.08% to 0.36%). The accessory minerals in green nephrite include zircon, rutile, titanite and apatite which indicate the magmatic origin. According to petrographic study, several processes have been found in green nephrite: Di→Dol, Tr→Di, Tr→Tr, Chl→Tr. The homogenization temperatures for the inclusions in tremolite in green nephrite range from 200 to 400℃. Test data of the stable isotopes of the ore-forming fluid acquired at different temperatures show that the H and O isotopic values of green nephrite from the secondary deposit fall in the value range of existing marble-type nephrite, but are remarkably different from values of other serpentine-type nephrite deposits, as evidenced by a comparison with other types of nephrite deposits in the world. The results obtained by the authors show that green nephrite from secondary deposits was formed by contact metasomatism between magmatic rocks and marble, and that the ore-forming fluid was derived from magmatic hydrothermal fluid and precipitation.