Formula: K Na1.41 Y Si8 O23.13
Name: Monteregianite-(Y)
Unit cell: 9.512 23.956 9.617 90.0 93.85 90.0 , V=2186.47
Space group: P121/N1 (14)

Ghose S , Sen Gupta P K , Campana C F , American Mineralogist , 72 (1987) p.365-374, Symmetry and crystal structure of monteregianite, Na4K2Y2Si16O38.10H2O, a, double-sheet silicate with zeolitic properties, Note: Several bond lengths cannot be reproduced with this data, but the authors, no longer have the original data, so they cannot check