Formula: Mn12 Si20 O61 H18 Ca K
Name: Tamaite
Unit cell: 16.8146 25.2036 13.3866 90.0 90.0 90.0 , V=5673.09
Space group: PNMA (62)

Hughes J M , Rakovan J F , Bracco R , Gunter M E , American Mineralogist , 88 (2003) p.1324-1330, The atomic arrangemetn of the ganophyllite-group modulated layer silicates as, determined from the orthorhombic dimorph of tamaite, with the elusive 16.8 A, ganophyllite-group superstructure revealed, Note: signs of the y-coordinates for O24 and O25 have been changed