These two rocks with very different shapes sit alongside Sabino Creek in the Santa Catalina Mountains, Arizona. The difference in their shapes probably reflects their different origins. It’s probably a safe bet that the rounded rock was sculpted by the stream action of Sabino Creek. The squarish stone most likely fell here from the canyon walls above, which here feature rocks with that same sort of blocky shape. Also, it is composed of the very same type of rock, banded Catalina gneiss, that forms the walls of Sabino Canyon.