The research has dealt with mineral composition of the dislocation clays developed on the Prague fault. The Prague fault is a tectonic boundary between underlying clayey slates of Záhořany series and Skalka quartzite. The fault zone is filled with clay or sandy-silt to silty-sand matrix with scattered fragments of the surrounding rocks either slates or quart zite. Quartz, illite, kaolinite, chlorite, sporadic feldspar and gypsum were identified in powdered preparations by X-ray diffraction. The clay fraction of the taken samples is composed of illite, less kaolinite and sporadic chlorite and gypsum., Pavel Hájek and Martin Šťastný., and Obsahuje bibliografické odkazy