Willhendersonite, a new zeolite isostructural with chabazite

Peacor D.R.*, Dunn P.J.**, Simmons W.B.***, Tillmanns E.****, Fischer R.X.****  

*Department of Geological SciencesUniversity of Michigan, Ann Arbor, Michigan 48109

**Department of Mineral SciencesSmithsonian Institution, Washington, D.C. 20560Department of Earth Sciences

***University of New Orleans, New Orleans, Louisiana 70148

****Institut fiir Geowiss e n sc haften, J ohannes Guten berg-Un iversittitPostfach 3980, D-6500 Mainz, Federal Republic of Germany 

Abstract

Willhendersonite( KCaAl3Si3O1.2 5 HzO) is a new zeolite which is isostructuralw ithchabazite, (Ca,NaJ[AlzSi+Orz.] 6H2O. It occurs in the San Venanzo Quarry, Terni,Umbria, Italy in cavities of Quaternary lavas as "trellislike" twinned aggregates,a nd astabular 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 p a r a m e t e r s  a : 9 . 2 3 ( 2 ) , b : 9 . 2 1 ( 2 ) , c : 9 . 5 2 ( 2 ) A , a = 9 2 . 7 ( l ) , F : 9 2 . 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 are 2.18 and 2.20 g/cm3, respectively.W illhendersonite is optically biaxial with a = 1.505(3)F, = 1.511(3),y =1.517(3)a nd2V: 87(3)".The strongest lines in the diffractionp attern are: (d, III")9.16,100; 5.18, 30; 4.09, 40; 3.71, 30; 2.907, 60; 2.804, 50.