AM_Heulandite-Ca_2 Formula: Ca.793 (Si6.921 Al2.079) O18 Name: Heulandite-Ca Unit cell: 17.158 17.433 7.388 90.0 113.41 90.0 , V=2027.96 Space group: C12/M1 (12)

Mortier W J , Pearce J R , American Mineralogist , 66 (1981) p.309-314, Thermal stability of the heulandite-type framework: Crystal structure of the, calcium/ammonium form dehydrated at 483K