AM_Kostylevite Formula: K2 Zr Si3 O10 H2 Name: Kostylevite Unit cell: 6.565 13.171 11.727 90.0 90.0 105.26 , V=978.25 Space group: P1121/B (14)

Ilyukhin V V , Khomyakov A P , Shumyatskaya N G , Voronkov A A , Nevskii N N , Belov N V , Soviet Physics Doklady , 26 (1981) p.118-120, The crystal structure of the new natural zirconosilicate K4Zr2Si6O18*2H2O, Locality: Khibinsk massif, Kola Peninsula, Russia, Note: dimorphic with umbite, Note: y(O7) corrected