Bentonite clays find wide industrial application and rich in Montmorillonite which is nano- structured and nanoporous member of smectite group and the dominant constituent of a bentonite. The mineralogical and physico- chemical properties of bentonites are studied by some instrumental analyses such as FTIR, and BETBJH method. The FTIR analysis is used to compare the purity of various natural montmorillonite samples, namely S1 and S2. FTIR analysis reveals the absorptions due to Al.O.Si bending ( where Al is an octahedral cation) at 524 cm(-1), Si.O.Si Bending at 466 cm- (1), and Al.Al.OH Bending at 917 cm(-1) and these absorptions in turn indicate the presence of the dominant montmor- illonite. This method shows that the natural bentonites contain non- smectite phases in both samples. BET ( Brunauer- Emmett- Teller) specific surface area and PSD ( Pore Size Distribution) analyses show that the external surface area of sample S2 measured by BET method ( ABET) ( m(2)/ g) is higher than that in S1 ( 17.4 to 14.4m(2)/ g) but S1 is more nano- porous than S2. At last but not least, the properties of some bentonites are studied through a combination of instrumental analyses namely FTIR, and BET specific surface area and BJH ( Barret- Johner- Halenda) pore size distribution analyses ( BET- BJH analyses).