The structural relation between svetlozarite and dachiardite

AbstractSvetlozarite, previously described as a new member of the mordenite group of zeolites, is reinterpreted as a multiply twinned and highly faulted dachiardite. X-ray diffraction study and transmission electron microscopy revealed (001) twins and (100) stacking faults. The former are attributed at least mainly to the insertion of a bglide plane between dachiardite sheets at each twin interface, which preserves the 5-ring linkages between the sheets. The latter are associated with loss of the Cface-centring relation, and are attributed to replacement of shared 5-rings by linked 4-rings in the dachiardite sheets. Further study is needed to determine whether the structural faults in the dachiardite structures are chemically controlled.