Gemological characterisation of yellowish-green montebrasite

Abstract Montebrasite is a rare gemstone whose gemmological characteristics and identification methods have rarely been reported. In this paper, ten montebrasite gemstones were selected for nondestructive testing, including conventional gemmological testing, microscopic observation, X-ray fluorescence spectroscopy (XRF), laser-exfoliation inductively coupled plasma mass spectrometry (LA-ICP-MS), infrared spectroscopy, Raman spectroscopy, and UV-visible spectroscopy, etc., and the gemmological and spectroscopic characteristics of montebrasite were clarified, and a method was found that could The method of rapid and indirect semi-quantitative estimation of the F content of montebrasite faceted gemstones has been developed, and the chromogenic genesis of montebrasite has been postulated. The aim is to enrich the gemmological data related to montebrasite, to find a fast and accurate method to identify the different analogous and homogeneous end elements of montebrasite, and to improve the detection efficiency. The results of conventional gemmological tests show that the refractive indices of the montebrasite samples are in the range of 1.605-1.634. Substituting the data into the formula nγ = -0.0053 wt% + 1.6477 yields an F content of 2.59-3.34 wt%, which preliminarily confirms that all of the samples belong to the montebrasite end element.