Oxygen isotopic composition as an indicator of ruby and sapphire origin: A review of Russian occurrences

This study combines our own new and literature data on oxygen isotopic compositions of corundum from the Russian territory including deposits in Karelia, Ural, Baikal and Far East regions. Corundum and associated minerals from placer and lode deposits are discussed in this review. The oxygen isotopic compositions of the colored corundum commonly result from mixing of meteoric (including glacial), crustal (metamorphic–metasomatic), and mantle magmatic waters. The individual values closely match the oxygen isotopic values in the host rocks. This allows identification of the sources for placer corundum using the δ18O value as an important component for accurate diagnostics of the gemstones. Some corundum, especially from northwestern Karelia, has extreme isotopic characteristics (δ18O down to −26.3‰), which almost invariably indicate its source location.