AM_Na8Si[Si6O18] Formula: Na8 Si7 O18 Name: Na8Si[Si6O18] Unit cell: 7.18 7.18 7.18 87.26 87.26 87.26 , V=368.92 Space group: R-3 (148)

Fleet M E , American Mineralogist , 83 (1998) p.618-624, Sodium heptasilicate: A high-pressure silicate with six-membered rings of, tetrahedra interconnected by SiO6 octahedra: (Na8Si[Si6O18])