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How to Tumble Obsidian

Tumbling rocks in a rotary tumbler eliminates and polishes the rocks' naturally rough exterior to create shiny, attractive and amazingly detailed surfaces. Some rocks already have a glossy surface. Obsidian is a glass-like stone that can be difficult to polish because of its already smooth exterior. Adding plastic pellets to the final stages of the tumbling process enhances the appearance of polished obsidian. Including Ivory soap, a pure soap that does not have chemical additives that leave residue on the stones, washes away the grit used throughout the tumbling process.

Things You'll Need

Rotary tumbler
Water
4 oz. coarse abrasive grit
4 oz. medium abrasive grit
2 oz. pre-polish grit
1 oz. polish grit
Plastic pellets
1 bar Ivory soap
Knife

Instructions

- 1
  Add your obsidian rocks and 4 oz. coarse abrasive grit to the rotary tumbler. Cover the rocks and grit with water. Tumble the rocks for one week. Remove the water and grit. Wash the obsidian.
- 2
  Put the rocks and 4 oz. medium abrasive grit into the tumbler, again covering them with water. Run the tumbler for another week. Remove the water, grit, any sharp or broken rocks and rocks that are smaller than one-quarter inch. Wash the remaining obsidian.
- 3
  Add the rocks and 2 oz. pre-polish grit to the tumbler. Add the plastic pellets until the tumbler barrel is three-quarters full. Cover everything with water. Run the tumbler for 10 days. Remove the grit, pellets, water, any broken rocks and obsidian pieces that are smaller than one-quarter inch. Wash the remaining stones.
- 4
  Add the obsidian, 1 oz. polish grit, and plastic pellets to fill three-quarters of the barrel and water to cover everything. Run the tumbler for two weeks. Remove the grit, pellets, water and unwanted obsidian pieces. Wash the remaining stones.
- 5
  Add the remaining obsidian and plastic pellets to fill 3/4 of the barrel. Use the knife to shave one bar of Ivory soap into the barrel. Cover everything with water. Run the tumbler for a few hours. Once you have removed the pellets and soapy water, you should have smooth, clean obsidian stones with a high luster.

Rocks & Minerals