Photoluminescence Spectra of Chrysoberyls from Various Origins

Photoluminescence spectroscopy is widely applied in the fields of gemmology and mineralogy utilizing its non-destructive, high-sensitivity, and high-resolution features. Chrysoberyls from gem-mining regions such as Myanmar, Brazil, Sri Lanka, Tanzania and synthetic chrysoberyl samples were studied by non-destructive laser-induced photoluminescence spectroscopy and laser ablation-inductively coupled plasma-mass spectrometry. The experimental results demonstrate a high degree of similarity in the comparative photoluminescence spectra across all examined samples, manifested by the presence of two narrow R-lines that are predominantly attributed to the emissive properties of Cr ion. This characteristic signature not only facilitates the discrimination between natural and synthetic chrysoberyl samples but also provide information about natural samples' geological origin. In the collected spectra, peak positions of these R-lines varies across a small range of wavelengths; the origin-dependent nature of these variations may be helpful in identifying the geographic source of unknown samples. In particular, the R₂ line of synthetic chrysoberyl is positioned at the longest wavelength, while for natural chrysoberyl this line is found at the shorter wavelength. Comparisons between R-line peak wavelengths and corresponding element concentrations of samples revealed strong correlations between peak shifts of the R-lines and increases in alumina concentrations. These correlations suggest that the substitution of trace elements for aluminum crystal sites responsible for the R-lines peak shifts.