Single crystals of muscovite have been studied by x‐ray Berg‐Barrett topography. Remarkably sharp contrasting stripes exhibiting anomalous x‐ray contrast were observed. From a detailed study of these as well as rocking curve experiments, it is concluded that the contrast is due to the corrugation of basal planes of mica, as a consequence of irregularity in the slip. The relation between the corrugations and the elastic properties of muscovite is discussed.