THE CRYSTAL-CHEMISTRY OF NATURAL ZEOLITES

This is a review of new achievements in the field of crystal chemistry of natural zeolites after 1983. There are two new zeolites, willhendersonite and perliaite, and two new frameworks, those of partheite and goosecreekite; gobbinsite has the framework of gismondine, and gonnardite that of natrolite. Bikitaite has been shown to have a triclinic symmetry and an ordered (Si,Al) distribution. T-O-T angles of 180 degree are not present in dachiardite and in a variety of ferrierite. A new computing method has been devised to deduce the Al-content of the tetrahedra of a framework from T-O distances and T-O-T angles, because the contents obtained via Jones' linear relation are systematically too low. Newly assessed correlations between chemistry and genesis of zeolites raise intriguing problems on the possiblity of explaining these correlations.