Mineralogical properties of two specimens called swelling chlorite were examined by means of X-ray, thermal, infrared abscrption and chemical analysis. They give a 14.8 Åreflection and higher orders. Although their diffraction patterns are close to those of chlorite, the 14.8 Åreflection moves to 15.5 Åupon glycolation. They are interstratified minerals of chlorite with expandable layers. One specimen seems to be an interstratified mineral of chlorite and montmorillonite but the expandable layer of the other specimen is undoubtedly different from montmorillonite. The data obtained are discussed in comparison with earier data of the so-called swelling chlorites.