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

oleh: Nikita V. Chukanov, Anatoly N. Sapozhnikov, Roman Yu. Shendrik, Marina F. Vigasina, Ralf Steudel

Format: Article
Diterbitkan: MDPI AG 2020-11-01

Deskripsi

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 (SO<sub>4</sub><sup>2−</sup>, S<sup>2−</sup> and Cl<sup>−</sup> anions, S<sub>3</sub><sup>•−</sup>, S<sub>2</sub><sup>•−</sup> and SO<sub>3</sub><sup>•−</sup> radical anions, H<sub>2</sub>O, CO<sub>2</sub>, COS, <i>cis-</i> as well as <i>trans</i>- or <i>gauche</i>-S<sub>4</sub> neutral molecules have been identified. It is shown that S<sub>3</sub><sup>•−</sup> and S<sub>4</sub> are the main blue and purple chromophores, respectively, whereas the S<sub>2</sub><sup>•−</sup> yellow chromophore and SO<sub>3</sub><sup>•−</sup> 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.