Crystal Chemistry, Isomorphism, and Thermal Conversions of Extra-Framework Components in Sodalite-Group Minerals

Abstract

Isomorphic substitutions of extra-framework components in sodalite-group aluminosilicate minerals and their thermal conversions have been investigated using infrared, Raman, electron spin resonance (ESR), as well as ultraviolet, visible and near infrared (UV–Vis–near IR) absorption spectroscopy methods and involving chemical and X-ray diffraction data. Sodalite-related minerals from gem lazurite deposits (haüyne, lazurite, and slyudyankaite) are characterized by wide variations in S-bearing extra-framework components including SO42− and various polysulfide groups (S2·−, S3·−, S4·− radical anions, and S4 and S6 neutral molecules) as well as the presence of CO2 molecules. Heating at 700 °C under reducing conditions results in the transformation of initial S-bearing groups SO42− and S3·− to a mixture of S2−, HS−, S2·−, and S4·− and transformation of CO2 to a mixture of CO32− and C2O42− or HC2O4− anionic groups. Further heating at 800 °C in air results in the decomposition of carbonate and oxalate groups, restoration of the SO42− and S3·− groups, and a sharp transformation of the framework. The HS− anion is stable only under reducing conditions, whereas the S3·− radical anion is the most stable polysulfide group. The HS−-dominant sodalite-group mineral sapozhnikovite forms a wide solid-solution series with sodalite. The conditions required for the formation of HS−- and CO20-bearing sodalite-group minerals are discussed.

Bystrite, Na7Ca(Al6Si6O24)S52–Cl–: formula redefinition and relationships with other four-layer cancrinite-group minerals

“…Note that the acyclic cis -S 4 isomer is the most thermodynamically stable (Eckert and Steudel, 2003; Wong and Steudel, 2003; Rejmak, 2020). This molecule was also detected in a number of sodalite-group minerals from the Malo–Bystrinskoe deposit (Chukanov et al , 2020a, 2022a).…”

“…It was also shown (Chukanov et al, 2022a) that the conversion of SO4 2and S3 •into HScoupled with the conversion of CO2 into C2O4 2takes place in slyudyankaite and other sodalitegroup minerals from the Malo-Bystrinskoe deposit after their heating under reducing conditions (over the Fe-FeS buffer) at 700C. The byproducts of these transformations are S4, S4 •-, and S2 •-.…”

“…Raman spectroscopy is a sensitive tool used to detect polysulfide species (Eckert and Steudel, 2003;Chukanov et al, 2020aChukanov et al, , 2020bSapozhnikov et al, 2021;Chukanov et al, 2022aChukanov et al, , 2022bChukanov et al, , 2022cChukanov et al, , 2022d. Both bystrite and sulfhydrylbystrite show strong Raman bands corresponding to the S 5 2anion which is a yellow chromophore.…”

“…The assignment of Raman bands was carried out in accordance with data from Eckert and Steudel (2003), Steudel and Chivers (2019), Rejmak (2020) and Chukanov et al (2020aChukanov et al ( , 2020b2022a, 2022b, 2022d.…”

Structure Modulations and Symmetry of Lazurite-Related Sodalite-Group Minerals

“…Positions of bands and their assignments are given in Tables 1 and 2. The assignment of the bands was made based on data from [5,6,9,10,[21][22][23][24][25][26][27]. The IR spectra are dominated by strong bands of the aluminosilicate framework, and the Raman spectra are dominated by strong bands of the S 3…”