It’s crazy, I have been faceting and cabbing gems since I was a child, but never did tumbling. Wow, I can’t believe what I’ve been missing! I have 3, 3 lb barrels running at all times and just started running some larger rock in a 12 lb. tumbler. I recently finished a batch of Silver Sheen Obsidian and Opalized wood that I’m excited about. This material is soft and everything I read, was trying to dissuade me from even trying. I gave it a try and here are the results. The Obsidian being 5 to 5.5 and the Opalized Wood being 5.5 to 6 on the Mohs harness scale, I thought they would play together nicely. I skipped stage #1, and ran stage #2 for 23 days. I ran stage #3 for 12 days. Finally I polished them in Cerium Oxide for two weeks.