MINCRYST is an original interrelated combination of the Crystal Structure Database for Minerals, Subbase of Calculated Polycrystal Standards (Calculated Powder X-ray Diffraction Standard Subbase,...

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.

New data on the isomorphism of extra-framework components (including chromophores) in two- and multilayer minerals belonging to the cancrinite and sodalite groups, are obtained using chemical and single-crystal X-ray diffraction data as well as infrared, Raman, ESR, UV–Vis–near IR absorption and photoluminescence spectroscopy methods. It is shown that the blue color of these minerals may be due to CO₃^•− or S₃^•− radical anions, whereas yellow and pink shadings are typically due to the presence of S₂^•− radical anions and S₄^•− or S₄, respectively. Two kyanoxalite varieties are distinguished: (1) with predominantly acid oxalate groups and (2) predominantly neutral oxalate groups. Zundel cation H₅O₂+ and CO₂ molecules are shown to be typical impurities in nosean. The Zundel cation is also detected in kyanoxalite and in the 12-layer, cancrinite-related mineral marinellite. Wide isomorphic series involving substitutions of SO₄⁻ for SO₃²⁻ and CO₃²⁻, as well as OH⁻ for H₂O and F⁻, are common for eight-layer, cancrinite-group minerals with an afghanite-type framework.