Tumbling of gemstones is usually done in a slowly rotating drum including water and the stone itself. The degree of shape depends on how long the stone gets tumbled. Eventually the final polish is applied in a different machine that smoothens the surface by vibration. The tumbling process of the raw rock can take up to 10 days and with a bit of luck produces the nicest sized pocket-healingstones, aquarium gravel and stones for metaphysical altars or crystal grids.