AM_Heulandite_1 Formula: Si9 Al.33 Na.39 O25.14 H28.74 Name: Heulandite Unit cell: 17.649 17.98 7.412 90.0 116.22 90.0 , V=2110.03 Space group: C12/M1 (12)

Wust T , Stolz J , Armbruster T , American Mineralogist , 84 (1999) p.1126-1134, Partially dealuminated heulandite produced by acidic REECl3 solution: A chemical, and single-crystal X-ray study, Sample: REE293, Tetrahedral sites were refined as Si