AM_Biotite_5 Formula: Mg1.638 Fe.864 Al1.322 Ti.336 Si2.84 K O12 Name: Biotite Unit cell: 5.3175 9.212 19.976 90.0 95.09 90.0 , V=974.66 Space group: C12/C1 (15)

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, Sample: in the 2M1 setting