River Rock Gravel. **Due to variations in natural stone actual colors may vary. We offer a wide variety of river rock and crushed flagstone quarried right here in Tennessee, as well as crusher run, 57 gravel, masonry/leveling sand. Bulk materials be scooped or bagged for your convenience. River Rock Sizes. (Pea Gravel) 1 ... Jaw crushers are an excellent primary crusher when used to prepare rock for subsequent processing stages. Cone and gyratory crusher. These are also compression-type machines that crush material between a moving and a stationary piece of steel. The setting between the two pieces controls the output.