Contribution
Dachiardite from Hokiya-dake: evidence of a new topology
Quartieri, Simona; Vezzalini, Giovanna; Alberti, Alberto
European Journal of Mineralogy Volume 2 Number 2 (1990), p. 187 - 194
20 références bibliographiques
publié: Apr 5, 1990
manuscrit accepté: Dec 27, 1989
manuscrit reçu: Feb 28, 1989
DOI: 10.1127/ejm/2/2/0187
Abstract
Abstract A refinement of the crystal structure of dachiardite from Hokiya-dake, Japan, shows the presence (16 % modal abundance) of domains of the hypothetical structure called “modified” dachiardite by Merlino (1975, 1976) associated with domains of "normal" dachiardite. As in the Elba dachiardite, two acentric framework configurations are present with the same frequency in the Hokiya-dake dachiardite, so that the statistical symmetry C2/m is maintained. This feature is interpreted as a tendency - common to all zeolites - to avoid T-O-T angles of 180° in the topological C2/M symmetry of dachiardite. As with the related structures of mordenite and epistilbite, a remarkable Al-enrichment is found in the tetrahedra of the 4-membered ring.
Mots-clefs
zeolite • dachiardite • crystal structure • new topology • acentric domains