中国科学院南京地质古生物研究所机构知识库

Sichuan Longxi nephrite is important in ancient Shu (ancient Sichuan) jade culture. In order to get the basic mineral, chemical and spectroscopic characteristics of Sichuan Longxi nephrite with different colors, exploring its significant implications for identifying the jade color and alteration color of nephrite unearthed in Sichuan, lithologic thin section analysis, laser Raman spectroscopy, X-ray fluorescence spectroscopy and mu-XRF scanning were conducted on Longxi nephrite samples with different colors. The systematic field geological survey and sample collection shows that the color bands of Longxi nephrite outcrop have clear boundaries of grey black-green-white-green-gray black. The Longxi nephrite mainly comprises tremolite, containing a small amount of muscovite, calcite, apatite and other accessory minerals. The light bands contain calcite veins, and the dark bands contain relatively more accessory minerals. The Longxi nephrite samples in different colors have almost the same Raman spectra of tremolite with Raman peaks at 174, 228, 376, 392, 674, 935, 1 027, 1 061 cm(-1) and the single peak of hydroxyl at 3 675 cm i in the range of 3 600 similar to 3 700 cm(-1). None, characteristic Raman peaks of actinolite or graphite, indicate that the dark color of Longxi nephriteis not from dark-color minerals. The XRF analysis reveals that the main chemical compositions of Longxi nephrite samples are SiO2 (55. 20%0 similar to 57. 94%), MgO (24. 10%similar to 25. 00%), CaO (12. 60%0 similar to 13. 80%), Al2O3 (0. 39% similar to 1. 77%), and iron oxide (0. 25%similar to 0. 42%). FeO is the main iron oxide tested by the Fe-VOL05 titration method, and there is no significant correlation between the Fe2+ content and the colors of Longxi nephrite. The mu-XRF scanning results indicate that Si and Mg are relatively high in black-deep gray Longxi nephrite, and the contents of V and Cr are relatively high in green-white Longxi nephrite. The contents of common coloring elements in jade, such as Fe, Mn and Cu, do not vary in different color bands of Longxi nephrite. It further proves that V and Cr lead to the green color in Longxi nephrite. The analysis of spectral characteristics and coloring mechanism based on nondestructive identification can be fully applied to the comparative raw material study of ancient jade arte facts, providing scientific data for provenance research on jade material and jade culture of ancient Shu culture.