Synchrotron X-ray Rietveld study of perlialite, the natural counterpart of synthetic zeolite-L

The crystal structure of perialite from the Murun alkaline Massif, USSR was determined and refined in space group P6/mmm, with a 18.5432, c 7.5310 Angstrom . The framework type of this natural zeolite is the same as synthetic zeolite Linde-L. Extra-framework cation and water oxygen positions were located and show large differences with respect to the cation and water sites previously reported for synthetic zeolites K-L and Ba, K-L. A revised unit cell formula is suggested containing Tl, but this is an artefact due to the use of thallium salts in heavy liquid purification of the type specimen.