Four Treasures Reference Database
Record No. 28986
HFSE-enriched metamorphic blue sapphires: FTIR and trace-element study, and implications for heat-treatment detection
Journal Article
Krzemnicki, M.S., Cartier, L.E., Zhou, W., Lefèvre, P., Wälle, M., Wang, H.A.O. and Braun, J. (2026) HFSE-enriched metamorphic blue sapphires: FTIR and trace-element study, and implications for heat-treatment detection. Journal of Gemmology, Vol. 40, No. 2, pp. 142–156.
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gems, corundum, treatments.4, Sri Lanka.12, Madagascar.12, heat treatment, FTIR
This study examines sapphires naturally enriched in high-field-strength elements (HFSE) from metamorphic origins in Sri Lanka and Madagascar. These sapphires display distinctive chemical inhomogeneities and microscopic growth features, as well as variable FTIR spectra, often including a broad absorption band near 3300 cm–1. Some of the studied samples also show FTIR spectral characteristics and short-wave UV luminescence typically associated with heat-treated stones, although all were unheated. Our findings demonstrate that commonly used indicators—such as specific FTIR band patterns (mainly the 3309 cm–1 triplet) and chalky bluish white short-wave UV fluorescence—are not always reliable for identifying heat treatment. Accurate distinction between heated and unheated sapphires requires detailed microscopic examination combined with advanced trace-element analysis and spectroscopic techniques, including Raman micro-spectroscopy of inclusions such as zircon, goethite and diaspore.