Abstract Dickite has previously been reported in “varicolored clays” of different ages in the Central and Southern Italian Apennines and in Sicily. Recently, dickite has been observed to occur randomly in Cretaceous “varicolored clays” belonging to the Scabiazza sandstone formation in the Oltrepo Pavese area of the province of Pavia (Northern Apennines). Field observations, crystal-chemical characteristics (XRD and EDS analysis), morphological and fabric features (SEM observations) of the dickite platelets support an authigenic origin by precipitation from pore solutions. Controversial interpretations concerning the nature of such interstitial solutions, and the origin of dickite include: diagenetic squeezing in an almost closed chemical system during tectonic events; supergene origin in an open system, thermodynamically dependent on the physico-chemical characteristics of the solutions, which may be mixed with meteoric waters.