Explorer Series Starter TumblerA diamond in the rough? Turn ordinary rocks into beautifully polished gemstones with our National Geographic Rock Tumbler Kit. This starter kit is a great way to get kids, and adults alike, introduced to the popular hobby of rock tumbling. And it's so easy to usejust insert rocks (half pound bag included, or select your own small rocks), polishing grit, and water into the barrel; attach it to the tumbler base; and plug in the tumbler. With a little