D got me a rock tumbler for Christmas! He shortly regretted it because our house was filled with the constant sound of rocks rattling around and around. I, however, am quite fond of it! I set up a way to muffle the sound by putting it in a cardboard box and then putting a bunch of towels on top of it. There is still a constant clattering sound, but much reduced. Here are my rocks, before and after the polishing.
I love searching for rocks on the beach or on hikes. It's like finding treasures!