The present invention relates to a nonhydrated bentonite intimately contacted with a polypropene, polybutene, or mixtures thereof to provide a formable and shapable non-aqueous bentonite composition particularly useful as a water barrier. The bentonite composition can be extruded in the form of a rope, rod, sheet or the like and is sufficiently tacky for adherence to a wall or conduit, floor or roof in areas of potential water flow to prevent the seepage of water through the bentonite composition. In one embodiment, the bentonite composition includes a polypropene and a polybutene and an elastomer, such as butyl rubber, having sufficient resilience to stretch or expand with the expanding bentonite upon hydration and to aid in maintaining the structural integrity and cohesiveness of the composition. In another embodiment, the composition comprises bentonite, an elastomer, and any plasticizer compatible with the elastomer.