Tumblin'!

Tumbling of rocks as a lapidary technique for rock polishing usually requires a plastic or rubber-lined barrel loaded with a consignment of rocks, all of similar or the same hardness, some abrasive grit, and a liquid lubricant. Silicon carbide grit is commonly used, and water is a universal lubricant. The barrel is then placed upon slowly rotating rails so that it rotates. The optimal speed of rotation depends on the size of the tumbler barrel and materials involved. Vibratory finishing process can be used instead.