A rotary rock tumbler is a machine that can shape and polish rocks such as agate and jasper into beautiful tumbled stones. The operator places rough rock into the barrel of the tumbler along with abrasive grit and water, then seals the barrel. The machine turns the barrel on a pair of rollers and the rocks tumble in the barrel. The tumbling action and the grit smooth the rocks and round sharp points and edges. A sequence of progressively finer grits followed by a polishing step complete the process and yield brightly polished tumbled stones in about one month. Vibratory rock tumblers are similar but have a vibrating bowl instead of a rotating barrel. They are more expensive than rotary tumblers but they produce tumbled stones in less than 1/3 the time and are more economical to operate.