Geographic origin determination of gemstones relies on the quantitative measurement of trace-element abundances linked to specific geological environments. For gem corundum, including sapphire, origin determination remains challenging because many deposits formed under similar geological conditions and therefore exhibit similar trace-element compositions [1, 2]. As a result, robust geographic discrimination requires analytical techniques capable of providing sufficient trace-element data while maintaining high sensitivity and mass resolution to reliably detect and distinguish low-abundance elemental signatures.

This contribution presents the applicability of femtosecond laser ablation ionisation mass spectrometry (fs-LIMS) for trace-element chemical composition analysis relevant to sapphire origin determination using the Laser Mass Spectrometer – Gran Turismo (LMS-GT), a high-mass-resolution (m/∆m of up to 20,000) time-of-flight LIMS instrument with micro-metre spatial resolution [3]. The analysed sample was a beryllium-diffusion-treated yellow sapphire provided by the Swiss Gemmological Institute SSEF. The sample surface was gold coated to reduce surface charging upon laser irradiation [4]. Measurements were performed using spot-by-spot fs-LIMS chemical analysis combined with mass-selective beam blanking to improve detection limits [5].

LMS-GT resolves atomic ions from polyatomic species interferences, allowing detection of trace elements relevant for sapphire origin determination, including Mg, Ti, V, Cr, Fe, and Ga, with high mass accuracy. Relative element abundances derived from spot-wise-averaged fs-LIMS spectra show good agreement with published LA-ICP-MS datasets for sapphires from major geographic deposits.  This demonstrates that fs-LIMS can quantitatively reproduce compositional patterns in corundum even without the application of matrix-matched relative sensitivity coefficients (RSC) [6], while maintaining minimal sample consumption. These results highlight the potential of high-resolution fs-LIMS as an analytical technique for gemstone chemical analysis applicable for origin determination. The combination of micrometre-scale spatial resolution, high mass resolving power, and high trace-element sensitivity for more elements than used in analysis so far provides new opportunities for chemical characterisation of gem materials.

[1] Lee A. Groat, Gaston Giuliani, Jennifer Stone-Sundberg, Ziyin Sun, Nathan D. Renfro, Aaron C. Palke, G&G, 2019, 55.
[2] Mandy Y. Krebs, Matthew F. Hardman, David G. Pearson, Yan Luo, Andrew J. Fagan, Chiranjeeb Sarkar, Minerals, 2020, 10, 447.
[3] Reto Wiesendanger, Valentine Grimaudo, Marek Tulej, Andreas Riedo, Rustam Lukmanov, Niels Ligterink, Rico Fausch, Herbert Shea, Peter Wurz, J. Anal. At. Spectrom., 2019, 34, 2061.
[4] Salome Gruchola, Andreas Riedo, Peter Keresztes Schmidt, Coenraad P. de Koning, Luca N. Knecht, Marek Tulej, Frances Westall, Peter Wurz, J. Anal. At. Spectrom., 2023, 38, 1372.
[5] Salome Gruchola, Coenraad P. de Koning, Reto Wiesendanger, Peter Keresztes Schmidt, Andreas Riedo, Valentine Grimaudo, Rustam A. Lukmanov, Niels F. W. Ligterink, Marek Tulej, Peter Wurz, International Journal of Mass Spectrometry, 2022, 474, 116803.
[6] Luca N. Knecht, Salome Gruchola, Peter Keresztes Schmidt, Marek Tulej, Andreas Riedo, Peter Wurz, Science Advances, 2026, in prep.