AM_Birnessite_2 Formula: Mn O2.7 K.23 H3.7 Name: Birnessite Unit cell: 5.149 2.843 7.176 90.0 100.76 90.0 , V=103.20 Space group: C12/M1 (12)

Post J E , Veblen D R , American Mineralogist , 75 (1990) p.477-489, Crystal structure determinations of synthetic sodium, magnesium and potassium, birnessite using TEM and the Rietveld method, Sample: K-birn