Crystal Chemistry, Thermal and Radiation-Induced Conversions and Indicatory Significance of S-Bearing Groups in Balliranoite

Crystal-chemical features of a sulfide-bearing variety of the cancrinite-group mineral balliranoite from the Tuluyskoe lapis lazuli deposit, Baikal Lake area, Siberia, Russia, have been investigated using a multimethodic approach based on infrared (IR), Raman, and electron spin resonance (ESR), as well as ultraviolet, visible and near infrared (UV&ndash:Vis&ndash:near IR) absorption spectroscopy methods, luminescence spectroscopy, electron microprobe analysis, selective sorption of CO2 and H2O from annealing products, and single-crystal X-ray structure analysis. Holotype balliranoite and its sulfate analogue, davyne, were studied for comparison. The crystal-chemical formula of the studied sample from Tultuyskoe is Na5.4K0.1Ca2.4(Si6Al6O24)Cl2[(CO3)0.7(SO4)0.18S*0.95Cl0.1(H2O)0.16], where the content of the wide zeolite channel is given in square brackets: S* is total sulfide sulfur occurring as disordered S2&#9679:&minus:, cis- and trans-S4, S52&minus:, minor S3&#9679:&minus:, and HS&minus: groups. The presence of S52&minus: and HS&minus: groups, the absence of CO2 molecules, and the association with pyrrhotite and Fe-free pargasite indicate that the studied sample crystallized under highly reducing, low-temperature conditions, unlike holotype balliranoite whose formation was related to the Somma-Vesuvius volcanic complex, Italy. Irradiation of balliranoite from Tultuyskoe with X-rays results in the transformations of polysulfide groups other than S3&#9679:&minus: into S3&#9679:&minus: in accordance with the scheme: S52&minus: &rarr: S2&#9679:&minus: + S3&#9679:&minus:: 3S2&#9679:&minus: &rarr: 2S3&#9679:&minus: + e&minus:: S4 + S2&#9679:&minus: + e&minus: &rarr: 2S3&#9679:&minus:: S4 + S2&#9679:&minus: + e&minus: &rarr: 2S3&#9679:&minus:: S4 + S52&minus: + e&minus: &rarr: 3S3&#9679:&minus: (e&minus: = electron).