Bentonite is but one component of drilling mud. The primary ingredient is Barite or barium sulfate, which is the only sufate compound not soluble in water. Barite is used to provide a weighting additve to the mud and Bentonite because it swells up in water is used to provide bulk. Water weighs 8.8 pounds per gallon, but weighted with Barite it can be made to weigh up to 19 pounds per gallon so Barite and Bentonite can be heavy stuff. One other thing, drilling mud is considered hazardous waste partly because of these two ingredients, but if you ever have an upper GI (stomach) X ray, you get to drink the "Barium Cocktail) which is nothing but Barium Sulfate and water.. so..its hazardous waste put into the ground, but not when it is put into you.