Yes! Jasper, Quartz, Agate and Petrified Wood, just to name a few, are all fantastic options that will yield solid results. There are two things you want to look for in tumbling rocks: You want the rock to be hard enough to not break apart in the machine You want the rock soft enough that they will polish in a reasonable amount of time  Using the Mohs Hardness Scale, you should look for minerals and gemstones that range between a five and an eight. Also remember that it is important to tumble stones that have similar rankings on this scale. This ensures that the softer specimens don’t crumble.