Thames And Kosmos Rock TumblerThe Thames & Kosmos Rock Tumbler is a hands on science kit that lets you transform rough stones into smooth, polished gems. Designed for curious kids, hobbyists, and budding geologists, it includes everything needed to explore the rock polishing process from start to finish. As the tumbler rotates, gritty stones are gradually shaped and refined through multiple stages, helping users learn about erosion, mineral hardness, and the natural processes that