BENTONITE FOR CASTING AND PALLET INDUSTRIES sodium (Na), calcium (Ca), and aluminium (Al). For industrial purposes, two main classes of bentonite exist: sodium and calcium bentonite. The chemical formula of Bentonite is Al2H2Na2O13Si4 (Sodium) and Al2H2O12Si4 (Calcium) Characteristics : Naturally Hard, Controlled Particle size Available Packing Option : Lumps in Loose form 25 Kg / 50 Kg Bags 1MT Jumbo Bags