Gemmological Analysis on A Meionite

In this paper, the gemmological and spectroscopic characteristics of a colourless sample in the routine testing process were analyzed by using the gemstone laboratory testing instruments and modern testing equipments. The results show that the refractive index of the sample is 1.550-1.588, the birefringence is 0.038, and the relative density is 2.89 ± 0.02 g / cm³. A large number of directionally arranged acicular crystals can be seen through magnification observation, and short columnar crystals can be seen perpendicular to the acicular direction. The results of EDS show that the main chemical elements of the sample belong to the scapolite family, and the average Ma value is 10.14%. According to the infrared spectra and Raman spectra, the generation of spectral characteristic peaks is mainly due to the vibration mode and frequency of CO₃^2-, Si-O, Al-O and O-H groups, among which the Raman characteristic absorption peaks are at 448, 1 090 cm^-1 and 1 327 cm^-1. The absorption peaks of infrared fingerprint location feature are at 1 404, 1 516, 1 007, 853, 609, 544, 459, 413 cm^-1. The characteristic absorption peaks of infrared functional groups are at 2 939, 2 496, 2 612, 3 391 cm^-1.There is no obvious absorption peak in the visible region of UV-Vis absorption spectrum. The absorption peak at 312 nm may be related to the d-d electronic transition of Fe^{3 +} and Fe³⁺ - Fe³⁺ ion pairs. The main photoluminescence band is located in the center of 608 nm, with 558, 569, 588, 629, 650, 678, 698 nm shoulder peaks. According to the evidence provided above, the sample is a meionitea which is a rare gem variety.