Spectroscopic and Crystal-Chemical Features of Sodalite-Group Minerals from Gem Lazurite Deposits

Abstract

Five samples of differently colored sodalite-group minerals from gem lazurite deposits were studied by means of electron microprobe and wet chemical analyses, infrared, Raman, electron spin resonance (ESR) and UV-Visible spectroscopy, and X-ray diffraction. Various extra-framework components (SO42−, S2− and Cl− anions, S3•−, S2•− and SO3•− radical anions, H2O, CO2, COS, cis- as well as trans- or gauche-S4 neutral molecules have been identified. It is shown that S3•− and S4 are the main blue and purple chromophores, respectively, whereas the S2•− yellow chromophore and SO3•− blue chromophore play a subordinate role. X-ray diffraction patterns of all samples of sodalite-group minerals from lazurite deposits studied in this work contain superstructure reflections which indicate different kinds of incommensurate modulation of the structures.

Sapozhnikovite, Na8(Al6Si6O24)(HS)2, a new sodalite-group mineral from the Lovozero alkaline massif, Kola Peninsula

“…Analogous signals of S 2 were observed in the ESR spectra of other sodalite-group minerals (Chukanov et al, 2020b). However, S 2 spectra are undetectably broadened by radical dynamics and should be much more environmental dependent due to the interaction between splitted π* states of S 2 with different local environments (Rejmak, 2018).…”

“…A very weak signal with g = 2.008 corresponds to the S 2 radical anion. Analogous signals of S 2 were observed in the ESR spectra of other sodalite-group minerals (Chukanov et al, 2020b) and ultramarine analogs prepared from zeolites (Kowalak et al, 2007). Another weak signal with g = 2.001 may be assigned either to anionic vacancy (Vassilikou-Dova and Lehmann, 1990) or to the S -/H 2 S centers (Hausmann, 1966;Symons, 1999).…”

“…Na 5.52 K 0.35 Ca 1.99 )(Si 6.10 Al 5.81 Fe 3+ 0.09 O 24 )(SO 4 ) 1.97 Cl 0.11 •nH 2 O(Chukanov et al, 2020b), (b) nosean (Na 5.72 K 0.64 Ca 0.33 )(Si 6.43 Al 5.51 Fe 3+ 0.06 O 24 )(SO 4 ) 1.21 Cl 0.11 F 0.09 •nH 2 O (Chukanov et al, 2020a), both from the Laach Lake volcano, Eifel paleovolcanic region, Germany, and (c) S-free sodalite Na 7.98 (Si 5.80 Al 6.20 O 24 )Cl 2.22 from the Vishnevogorskiy syenite-miaskite complex, South Urals, Russia (Nishanbaev et al, 2016). The spectra are offset for comparison.…”

Multi-Technique Diagnostic Analysis of Plasters and Mortars from the Church of the Annunciation (Tortorici, Sicily)

“…Inclusions of several other minerals are also common, including pyrite (FeS 2 ), calcite (CaCO 3 ), diopside (CaMgSi 2 O 6 ), forsterite (MgSiO 4 ), and wollastonite (CaSiO 3 ), in varying amounts [38]. Lazurite itself is a member of the sodalite group, which includes sodalite, nosean, and hauyne, and is typically considered a sulfur-rich hauyne [39]. The sodalite minerals contain frameworks of alternating silica and alumina tetrahedra creating large cubo-octahedral cages, known as β-cages; extra-framework cations (Ca 2+ , K + , or Na + ), anions (Cl − , OH − , SO 4 2− , or Sn − ), and neutral species (H 2 O) are entrapped within these cages [39].…”

“…Lazurite itself is a member of the sodalite group, which includes sodalite, nosean, and hauyne, and is typically considered a sulfur-rich hauyne [39]. The sodalite minerals contain frameworks of alternating silica and alumina tetrahedra creating large cubo-octahedral cages, known as β-cages; extra-framework cations (Ca 2+ , K + , or Na + ), anions (Cl − , OH − , SO 4 2− , or Sn − ), and neutral species (H 2 O) are entrapped within these cages [39]. Lazurite's blue color is attributed to sulfur polyanion radicals trapped in the β-cage structure.…”