Bentonite particles are widely used for different applications such as drilling fluid, bleaching earth, catalyst, nanoclays, etc. Bentonite is rich in Montmorillonite, which is a nanostructured and nanoporous clay mineral. To characterize bentonite it is important to distinguish different components of clay mineral admixtures from each other and to obtain information regarding their structure, composition, and structural changes. In this research, bentonites are first screened and purified using sedimentation through dispersing 13% concentrations of bentonites in deionized water. FTIR spectroscopy along with other characterizing method such as x-ray diffraction and x-ray fluorescence is used for characterization of bentonites. Adsorption peaks at 524, 466, and 917 cm(-1) confirm the presence of montmorillonite. The broadness of 3623 cm(-1) peak shows the isomorphic substitution of octahedral Al3+ by Fe2+ or Mg2+ cations which affects the type and properties of studied bentonites. For samples S3 and G1, most of the quartz (793 cm(-1)) is settled in U.F.2 (underflow 2). The amount of montmorillonite decreases in U.F.2. The decrease in quartz is observed in O.F.1 (overflow 1) and especially in all O.F.2 (overflow 2) samples. This result is in agreement with XRD patterns. This research aims at using FTIR technique along with other complementary methods in the characterization of bentonites.