AM_Mountainite Formula: K Na2 Ca2 Si8 O26 H2.44 Name: Mountainite Unit cell: 13.704 6.576 13.751 90.0 105.752 90.0 , V=1192.67 Space group: P12/C1 (13)

Zubkova N V , Pekov I V , Pushcharovsky D Y , Chukanov N V , Zeitschrift fur Kristallographie , 224 (2009) p.389-396, The crystal structure and refined formula of mountainite, KNa2Ca2[Si8O19(OH)]*6H2O, Locality: Yubileinaya pegmatite, Lovozero alkaline complex, Kola Peninsula, Russia