Three bentonites from Turkey were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), differential thermal analysis (DTA), thermogravimetric analysis (TG), Fourier transform infrared (FT-IR), magic angle spinning nuclear magnetic resonance (MAS NMR) and surface area measurement techniques. The XRD patterns showed that all three bentonite samples (B1, B2 and B3) were mainly composed of montmorillonite accompanied by cristobalite. In addition, albite appears in B3 sample studied. The heats of immersion of the bentonite samples (B1, B2 and B3) measured with a Calvet calorimeter at 30 degrees C in water were determined as -75.70, -54.69 and -68.22 J/g, respectively. (C) 2010 Elsevier B.V. All rights reserved.