The Gemological And Mineralogical Characteristics Of Turquoise From Luo Nan,Shan Xi

Turquoise output from Luo Nan,Shanxi,which is a site of turquoise,may be an origin of the ancestor's turquoise products in Neolithic time.In this paper,EPMA,infrared spectroscopy,Raman spectroscopy,UV visible spectroscopy,polarizing microscope,SEM,XRD,differential thermal analysis experiments were performed to study the gemological characteristics of the turquoise samples from Luo Nan,Shan Xi.And LA-ICP-MS experiment is used to analyze the content of trace elements and generate REE partition.Then using these experiments results,combined with references,to infer which sites the turquoise from Luo Nan,Shan Xi may go to.The results of EPMA experiments show that the content of CuO is lower than the theoretical value,while the content of P₂O₅ is basically higher than the theoretical value,and the content of Al2O3 is between 34³8%.Differential thermal analysis showes that planar water,crystal water and consititution water have been lost under 400?.Being observed under polarizing microscope and SEM,turquoise from Luo Nan,Shan Xi is associated with a large number of quartz.Limonite and chalcedony can be seen in some samples.Also some quartz veins is distributed in black ocks.The main structure of turquoise is cryptocrystalline;but annular structure and nodular structure can be partly observed.The turquoise crystallites are mostly plate shape,flake shape and irregular mass shape.Pore distribution can be seen in some samples.With more xenomorphic of the crystallite,and fewer pores,more uniform of the arrangement,then the structure is more compact,which makes turquosie appear block structure.Conversely,the turquosie appears botryoidal structure.Results of X-ray diffraction show all the samples contain turquoise and quartz,some samples contain small amounts of illite and kaolinite.The results of infrared spectrum and Raman spectrum show that the spectral characteristics of natural turquoise are caused by the vibration of three groups:OH,H₂O and PO₄^3-.The UV Vis spectra results shows that with the higher content of Cu ion in turquoise,the absorption peak of Cu²⁺d-d transition would be more obvious,and the color is blue;yet with the increase of content of Fe³⁺,the absorption peak of 430nm broadens,and the color becomes yellowish green.The results of LA-ICP-MS show that content of REE in turquoise from Luo Nan,Shan Xi is low,which differs from 0.26 to 7.87ppm.And content of LREE is higher than HREE.Differentiation of LREE and HREE is not obvious.And anomalies of Eu and Ce are not obvious,both?Eu and?Ce were around 1.With being compared with these values of turquoise from Jia Hu Site in Wu Yang and Erlitou site in Yan Shi,it is inferred that Luo Nan,Shan Xi might be one source of Jia Hu site in Wu Yang,but not of Erlitou site in Yan Shi.