A Comparison of R-line Photoluminescence of Emeralds from Different Origins

A fundamental task for gemmologists is determining whether an emerald is natural or synthetic. Within the laser-excited photoluminescence spectrum of emerald, the peak positions and relative intensities of two emissions in the 680–685 nm range, known as R lines, can help identify if a sample is natural, and can also provide information about its geological origin. In particular, the R1 line of synthetic emerald is positioned at the shortest wavelength, while for natural emeralds with a non-schist origin this line is found at the same or longer wavelengths, and for schist-type emeralds the line peaks at an even longer wavelength. This measurement can supplement origin results obtained from established methods, such as inclusion microscopy, spectroscopy (e.g. ultraviolet-visible–near infrared [UV-Vis-NIR], Fouriertransform infrared [FTIR] and Raman) and trace-element analysis by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS).