A new complex polytype of biotite has been examined by High Resolution Transition Electron Microscopy (HRTEM). The polytype can be written as [0 (22) 6202 (22) 3] or [0 (22) 6202 (22) 3], using the RTW notation (Ross et al. 1966). It was confirmed that the polytype has 2M1 stacking with only two type I°2 intrinsic faults (Baronnet et al. 1981) in one unit.
