Crystal structure of chlorinated mineral of cancrinite group with bystrite-type framework

Abstract

The formula of chlorinated bystrite (rare mineral of cancrinite group) has been refined to Na_7.22Ca_0.92[Al₆Si₆O₂₄](S₅)_0.94Cl_1.01. The X-ray diffraction data on the contents of chlorine and sulfur in this mineral are confirmed by the results of chemical analysis. The bystrite cage is found to contain a (S₅)²–cluster, which is elongated along the c axis and has a chain configuration. Different ways of aggregation of sulfur atoms lead to cis- and trans-configurations of chains. Columns of cancrinite cages contain–Ca–Cl–Ca–Cl–chains, which were observed previously in the structures of minerals of davyne subgroup, afghanite, and tounkite.