Rock Tumblers

I've got a daughter who is obsessed with rocks, she has been since she was able to start picking them up off the ground and bringing them home with her. So something I've thought about getting her is one of the cool rock tumblers they sell at Hobby Warehouse. I think she'd have a great time polishing up all the rocks she has stored in her bedroom and then she'd be off to find even more to add to her collection.