AM_Cordierite_12 Formula: O18.6 Al3.84 Be.16 Si5 (Mg1.4 Fe.6) Na.25 H.6 Name: Cordierite Unit cell: 17.06 9.759 9.322 90.0 90.0 90.0 , V=1552.01 Space group: CCCM (66)

Armbruster T , American Mineralogist , 71 (1986) p.746-757, Role of Na in the structure of low-cordierite: A single-crystal X-ray study, Sample: from Alpe Sponda, Central Alps, Switzerland