AM_Helvine_1
Formula: Mn3.88 O12 Be3 Si3 S
Name: Helvine
Unit cell: 8.291 8.291 8.291 90.0 90.0 90.0 , V=569.93
Space group: P-43N (218)

Hassan I , Grundy H D , American Mineralogist , 70 (1985) p.186-192, The crystal structures of helvite group minerals, (MnFeZn)8(Be6Si6O24)S2