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
published: Apr 17, 1990
manuscript accepted: Dec 27, 1989
manuscript received: Feb 28, 1989
ArtNo. ESP147050202005, Price: 29.00 €
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.