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-Vis-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)Cl-2[(CO3)(0.7)(SO4)(0.18)S*Cl-0.95(0.1)(H2O)(0.16)], where the content of the wide zeolite channel is given in square brackets; S* is total sulfide sulfur occurring as disordered S-2(?-), cis- and trans-S-4, S-5(2-), minor S-3(?-), and HS- groups. The presence of S-5(2-) and HS- 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 S-3(?-) into S-3(?-) in accordance with the scheme: S-5(2-) & RARR; S-2(?-) + S-3(?-); 3S(2)(?-) & RARR; 2S(3)(?-) + e(-); S-4 + S-2(?-) + e(-) & RARR; 2S(3)(?-); S-4 + S-2(?-) + e(-) & RARR; 2S(3)(?-); S-4 + S-5(2-) + e(-) & RARR; 3S(3)(?-) (e(-) = electron).