Bentonite is a clay mineral predominantly consisting of mineral Montmorillonite mixed with some related minerals 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.
The Bentonite found in the Kutch region of India is of igneous origin. It was formed millions of years ago, possibly from the volcanic ash falling in stagnant saline water in semi-arid conditions. Due to the natural characteristics of these particular volcanic ashes, the chemical composition of this Bentonite is somewhat different from the Bentonite available in the rest of the world. Most of these deposits are of natural sodium Bentonite with higher iron content which gives them their darker colour. Due to very fine particle size, this Bentonite shows extra-ordinary swelling capacity and bonding powers. These differences mean that the Bentonite finds the most number of uses in various industries throughout the world.