Bentonite is a clay mineral predominantly consisting of mineral like Nontronite and Beidellite. These are three layered Aluminosilicate with molecules of water between layers. For natural Sodium Bentonite, exchangeable sodium cations are predominant, rather than other cations like calcium, magnesium etc. Similarly in Calcium Bentonite, calcium cations are predominant. In fact in all Bentonite available in the world, the sodium variety has high swelling and gelling properties along with good viscosity and liquid limit.