CRYSTAL CHEMISTRY OF CANCRINITE-GROUP MINERALS WITH AN AB-TYPE FRAMEWORK: A REVIEW AND NEW DATA. II. IR SPECTROSCOPY AND ITS CRYSTAL-CHEMICAL IMPLICATIONS

摘要

We present a comparative analysis of powder infrared spectra of cancrinite-group minerals with the simplest framework, of AB type, from the viewpoint of crystal-chemical characteristics of extra-framework components. We provide IR spectra for typical samples of cancrinite, cancrisilite, kyanoxalite, hydroxycancrinite, depmeierite, vishnevite, pitiglianoite, balliranoite, davyne and quadridavyne, as well as the most unusual varieties of cancrinite-subgroup minerals (Ca-deficient cancrinite, H_2O-free cancrinite, intermediate members of the series cancrinite – hydroxycancrinite, cancrinite–cancrisilite, cancrinite–kyanoxalite, K-rich vishnevite, S_2-bearing balliranoite). Samples with solved crystal structures are used as reference patterns. Empirical trends and relationships between some parameters of IR spectra, compositional characteristics and unit-cell dimensions are obtained. The effect of Ca content on stretching vibrations of CO_3~(2–) is explained in the context of the cluster approach. The existence of a hydrous variety of quadridavyne is demonstrated.