AM_Heulandite_3 Formula: Si9 Al.283 Na.19 O20.12 H12.9 Name: Heulandite Unit cell: 17.583 17.695 7.408 90.0 116.52 90.0 , V=2062.34 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: DEHY323, Tetrahedral sites were refined as Si