AM_Biotite_4 Formula: Mg1.638 Fe.864 Al1.322 Ti.336 Si2.84 K O12 Name: Biotite Unit cell: 5.3204 9.21 10.104 90.0 100.102 90.0 , V=487.43 Space group: C12/M1 (12)

Ohta T , Takeda H , Takeuchi Y , American Mineralogist , 67 (1982) p.298-310, Mica polytypism: Similarities in the crystal structures of coexisting 1M and, 2M(1) oxybiotite