- Rough material from ¾ to 3 inches for tumbling and small cabbing projects
- Sold by the pound
Obsidian is volcanic glass formed when lava cools so quickly that few or no large crystals have time to form. It’s been a favorite material for chipped stone artifacts since our ancestors started stone flaking.
Obsidian is a popular stone for tumbling because it is softer than many agates and jaspers and the pieces wear into beautiful smooth shapes quickly during the first stages. It’s much easier to get flawless finished stones with obsidian as imperfections on the surface have easily eroded away from the tumbling.
Our black obsidian is a transparent to translucent material that is mostly pure black. It is the classic obsidian. Chips and imperfections show up more easily on black obsidian, but we grade most of those out. A bowl full of tumble-polished black obsidian is a thing of beauty. Black obsidian also lends itself to jewelry use due to the stark purity of the color.
All our obsidian tumbling material is graded as a select byproduct of cleaning stone for flintknapping sales. Accordingly, this is some of the best graded obsidian for tumbling you will ever see. This is not the ordinary crushed and broken material commonly sold for tumbling, rather each individual piece is selected for shape, thickness, and color as well as the absence of cracks. All material is cleaned with small copper billets and never felt a steel hammer.
All types of obsidian are sensitive to having harder stones in a tumbler load, so should be tumbled alone with small media added for cushioning. In addition to the four stages used for tumbling agates and jaspers, an additional stage with cerium oxide can produce a fantastic polish. A combination of rotary for phase one and two and vibratory for stage three and four works well, but the entire process can be done in a rotary tumbler with media for cushioning.
If you like to tumble polish stones, you should master obsidian. Obsidian is good for specimens, jewelry, wire wrapping and metaphysical stones. It cuts nice cabochons and is not as hard as agate, jasper, or most other quartz stones.