Study on Spectroscopy of Sphene From Pakistan

As a precious gem, sphene features sound characteristics of gemology and outstanding brilliance, enjoying great popularity in Europe, United State, Japan and India. As the communication between domestic and overseas jewelry market has been increasing in recent years, some Chinese regions are also witnessing increased popularity of such a gem with a brilliant appearance. However, domestic research on gem-level sphene is quite a few, with relevant recognition being limited to refractive index, chromatic dispersion and other basic properties of mineralogy. There is a big gap in terms of the study on its spectroscopy feature and color formation reasons. On the basis of analyzing the constituent analysis of yellow-green sphene, this paper summarizes characteristics of its infrared spectroscopy, Raman spectrum and ultraviolet-visible spectrum. According to the LA-ICP-MS test on sphene samples, it finds that the major element content of samples of this batch is stable. Among them, the content of TiO2 is 35. 42 Wt%, and the content of MnO and Cr2O3 is quite low (0. 04 Wt% and 0. 01 Wt% respectively). Therefore, this batch's color of sphene sample is mainly related with Fe, the element of high content. The scope of fundamental frequency 400-1 200 cm i of infrared vibration could witness the absorption peak resulting from Si 0 and Ti 0 vibration. Meanwhile, the absorption width that existed in Fe' could be found at 6 800 cm 1. The test result of the Raman spectrum (45 1 500 cm 1) is basically in line with previous studies. It is speculated that the weak Raman spectrum is related to Fe. On the basis of the comparison of Raman spectrum results of cutting sample GS-1 in 5 different directions, it finds that the location of Raman spectrum in different crystal faces keeps unchanged, but the relative strength of some vibrations varies. As shown by the ultraviolet-visible spectrum peak-differentiating and imitating, the absorption at 14 461 cm i might be derived from the d d forbidden transition of Fe' within octahedron, but the three absorption peaks of 15 887, 16 781 and 17 781 cm i have resulted from the d d forbidden transition of Fe3+ within octahedron. Innovations of this research can be summarized into two aspects as below: ( 1) it systematically summarizes characteristics of infrared spectroscopy, Raman spectrum and ultraviolet-visible spectrum of gem-grade sphene and makes analyzes based on the constituent test result; (2) Relevant software is applied to make peak-differentiating and imitating on the ultraviolet-visible spectrum of sphene samples. Absorption peaks are assigned in accordance with locations of spectrum peaks, relative strength, peak shape characteristics and principles summarized by previous researchers. In the end, it raises that Fe might be the cause for the color development of gem-grade yellow-green sphene.

Automated summary

Sphene, a precious gem with outstanding brilliance, is popular in Europe, United States, Japan, and India. However, domestic research on gem-level sphene is limited, lacking in-depth study on its spectroscopy features and color formation reasons. This research analyzes the characteristics of infrared spectroscopy, Raman spectrum, and ultraviolet-visible spectrum of gem-grade sphene, identifying Fe as the major element influencing its color development.