Boulder-sized clasts are discovered in some stratified rocks, such as rugged empire and also rock clay. In geology, a boulder is a rock fragment with size higher than 256 millimetres (10.1 in) in size. While a rock may be small sufficient to relocate or roll manually, others are incredibly large. In common use, a rock is also large for an individual to move. Smaller sized stones are normally just called rocks (American English) or stones (In British English a rock is bigger than a stone).