For the first time, a periodicity of 14 Angstrom is recognized as a typical modulation period in metakaolinite. Energy-filtered electron diffraction data confirm that dehydroxylation does not occur abruptly in kaolinite. The degree of ordering becomes much lower during the progression of dehydroxylation in metakaolinite than in kaolinite. However, different types of modulations, with periods in the range from similar to1.4d(001) (9.47 Angstrom) to 2.9d(001) (19.89 Angstrom), form along the c*-axis in metakaolinite. Modules (14.2 Angstrom = 2.1d(001)) that have a length that is approximately twice as long as the metakaolinite layer (6.86 Angstrom) are the most common. Presumably, the remnant oxygens and vacant anion sites rearrange to acquire stability in the layer structure, which builds modulations along the c*-axis in the metakaolinite.