Characterization of synthetic and natural gold chalcogenides by electron microprobe analysis, X‐ray powder diffraction, and Raman spectroscopic methods

• Published in: Journal of Raman Spectroscopy
• Main Authors: Palyanova, Galina, Beliaeva, Tatiana, Kokh, Konstantin, Seryotkin, Yurii, Moroz, Tatyana, Tolstykh, Nadezda
• Other Authors: Russian Foundation for Basic Research
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: Kamchatka
• Online Access: http://dx.doi.org/10.1002/jrs.6327; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jrs.6327; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jrs.6327

Abstract Electron microprobe analysis (EMPA), X‐ray powder diffraction (XRD), and Raman spectroscopy (RS) were applied to characterize the synthetic gold chalcogenides of the Au–Te–Se–S system and natural analogs from the Gaching deposit (Central Kamchatka, Russia). The EPMA results showed that the synthetic chalcogenides have different Te/Se/S and Au/X (X = Te + Se + S) ratios: AuX 2 , Au 3 X 10 , and AuX. They are similar in composition to natural compounds — calaverite (AuTe 2 ), maletoyvayamite (Au 3 Te 6 Se 4 ), and unnamed minerals AuTe 0.7 Se 0.3 and AuSe 0.7 S 0.3 . It was established that chalcogenides AuX, Au 3 X 10 , and AuX 2 have a specific Raman spectra with characteristic peaks. The position of the peaks and the character of the spectra of the synthetic phases and their natural analogs from the Gaching deposit coincide within the limits of accuracy. Different ratios of chalcogenes Te/Se/S in compounds influence the Raman peak positions. The positions of the peaks for natural compounds AuX differ depending on the predominance of Te (AuTe 0.7 Se 0.3 ) or Se (AuSe 0.7 S 0.3 ). AuSe synthetic phases consist of a mixture of α‐ and β‐polymorphs. Raman spectroscopy can be used for the identification of natural gold chalcogenides worldwide, which are difficult to diagnose by other methods due to the microscopic grain sizes and close intergrowths with other ore minerals. The similarity of the Raman spectra upon changing the concentrations of Se and S suggests identical structures and possible isomorphism in the composition range of AuTe 0.7 Se 0.3 – AuTe 0.7 Se 0.2 S 0.1 , AuTe 1.9 Se 0.1 – AuTe 1.8 Se 0.1 S 0.1 , and Au 3 Te 6 Se 4 – Au 3 Te 6 S 3 Se.