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

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. [ABSTRACT FROM AUTHOR]