AM_Topaz_1 Formula: Al2 Si O4 F2 Name: Topaz Unit cell: 4.652 8.801 8.404 90.0 90.0 90.0 , V=344.08 Space group: PBNM (62)

Northrup P A , Leinenweber K , Parise J B , American Mineralogist , 79 (1994) p.401-404, The location of H in the high-pressure synthetic Al2SiO4(OH)2 topaz analogue, Sample fluor-topaz from a Mexican rhyolite