Characterization of chrysoberyl and its gemmological varieties by Raman spectroscopy

• Published in: Journal of Raman spectroscopy 2023-08, Vol.54 (8), p.857-870
• Main Authors: Rybnikova, Olena, Bačík, Peter, Uher, Pavel, Fridrichová, Jana, Lalinská‐Voleková, Bronislava, Kubernátová, Monika, Hanus, Radek
• Format: Article
• Language: English
• Subjects: Alexandrite; chrysoberyl; Corundum; cymophane; Gems; Inclusions; Luminescence; photoluminescence; Raman spectroscopy; Sample preparation; Spectroscopy; Spectrum analysis
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.6566

Various chrysoberyl varieties (non‐phenomenal chrysoberyl, alexandrite and cymophane) are gemstones of high demand; therefore, they are subjected to numerous substitutions by other materials and synthetic analogues. To address this issue, non‐destructive methods for studying gemstones are highly sought after. Raman spectroscopy is one of the most suitable non‐destructive methods for studying gemstones as it requires no sample preparation and does not leave any price‐reducing signs on the gemstone surface. The research is focused on Raman spectroscopy application on chrysoberyl identification, differentiation between its varieties, inclusion analysis, and detection of synthetic analogues and imitations. The alexandrite variety can be identified by its broad luminescence band that ranges from 640 to 790 nm (15 625–12 658 cm−1). Synthetic alexandrite has sharper and more intensive bands on the luminescence spectrum, especially 690 and 696 nm (14 492–14 367 cm−1). Rutile inclusions can be distinguished by a broad band 580–640 cm−1 in the Raman spectrum. Imitations of chrysoberyl represented by corundum and colour‐changing spessartine was also identified. The orientation of faceted stones can also be determined by specific bands present in the Raman spectrum. Various chrysoberyl varieties (non‐phenomenal chrysoberyl and alexandrite, cymophane) have been analysed by means of Raman spectroscopy in order to identify mineral species, discriminate chrysoberyl varieties, study inclusions and detect synthetic analogues and other mineral imitations. The work confirms the ability of Raman spectroscopy (classical Raman spectra and photoluminescence) to cope with the objectives and even more to assume qualitative chemical composition and faceted crystal orientation and identification of crystallographic axes.