Willhendersonite, a new zeolite isostructural with chabazite

Abstract

Willhendersonite (KCaAl3Si3O12 . 5HzO) is a new zeolite which is isostructural with chabazite, (Ca,NaJ[AlzSi+Orz] . 6H2O. It occurs in the San Venanzo Quarry, Terni, Umbria, Italy in cavities of Quaternary lavas as trellislike twinned aggregates, and as tabular crystals in a limestone xenolith from the Ettringer Bellerberg near Mayen, Eifel, Germany. It is triclinic, space group PT. Single crystals from Mayen have the unit cell parametersa:9.23 (2),b:9.21(2),c: 9.52(2)A,a=92.7( l),F:92.4(l),7:9 0.1(l),y = 808A3, Z = 2. Willhendersonite is colorless and transparent, and it has a vitreous luster. The Mohs' hardness is 3. The measured and observed densities are2.l8 and2.20 glcm3, respectively. Willhendersonite is optically biaxial with a = 1.505(3), F = 1.511(3), y = 1.517(3) and2V: 87(3).The strongest lines in the diffraction pattern are: (d, III)9.16, 100; 5.18, 30; 4.09, 40; 3.71, 30; 2.907, 60; 2.804, 50.