Citation: Takeda, H.; Ross, M. (1975). Mica polytypism: Dissimilarities in the crystal structures of coexisting 1M and 2M1 biotite. American Mineralogist, 60, pp. 1030-1040.
Formula: Al1.999 K0.5 Mg2.001 O12 Si3
List type: interleaving
List: 2D
Basis: (1;0;0 0;1;0)
Dimensionality: 2
Formula: Al14 Mg6 O24 Si8 (Al7 Mg3 O12 Si4)
Multiplicity: 1