Abstract: An expansion fracture device for fracturing rocks and the like and having a rod, threads at least one end, a conduit in at least one end extending inwardly along the rod, and outwardly to the exterior of the rod. Collars are located at each end, defining axially opposed sealing faces directed towards one another, each of the opposed faces defining generally axially disposed tapering recesses. An expandable sleeve member formed of resilient plastic material surrounds the rod, and has two ends, each end defining generally tapering surfaces adapted to fit within respective tapering recesses defined by the axially opposed surfaces of the collars.