The machine works great with most common landscaping rock — river rock, pea gravel, crushed granite, decorative stone, and lava rock. It's designed to separate dirt and fine debris from rocks roughly 3/4 inch and larger. If you have very small gravel (like pea-size), it still works but the screen may let some smaller pieces through with the dirt. Text us if you're unsure — we can advise based on your rock type.