Add to ORKGAbstract--Classification and identification criteria of maximum-degree-of-order (MDO) polytypes of homo- and meso-octahedral micas based on the distribution of the intensities of 201 (13l) and 021 reflections are proposed. Calculated IF(20/) [ 2 and [F(02I) [ 2 values for single crystals of micas with different compositions are given for one-, two-, and three-layer polytypes. Transmission powder diffrac-tometry is proposed as a suitable method for the identification fthe different groups of mica polytypes from polycrystalline specimens. Calculated powder patterns and the characteristic properties of the dif-fraction patterns of random and highly oriented aggregates are employed for identification purposes. The individual MDO polytypes are d...