Stones are polished by tumbling them around inside a rock polishing machine barrel filled with water and polishing grit. A variety of course silicone carbide powdered grits are applied, each designed to smooth the stones further with each application, rubbing away the rough stone surface in order to give the stone a polished shine.
- Load the rock polishing machine
Fill the rock polishing machine barrel about three-fourths full with the stones that you wish the polish. The stones should be under 1 inch in diameter and of the same hardness to avoid crushing softer stones with harder stones in the mix. One or two larger stones can be added to the smaller stone mix if desired. Shake the barrel to settle the stones on the bottom. Pour water into the barrel until it covers the stones, and then add 80-grit powder to the water, using about 1 tablespoon for a barrel of 1.5 pounds. Place the top onto the barrel tightly.
- Tumble the stones
Start the rock polishing machine to begin tumbling the stones. The grit will run over the surfaces of the stones, smoothing down the rough surfaces slightly. Run the machine for three to 10 days, checking the stones periodically. Softer stones will take less time. When the stones appear to not be getting any smoother, stop the machine, and clean the stones and barrel of the grit.
- Continue polishing
Place the stones back into the barrel. Add a 220-grit powder and enough water to cover the stones. Run the machine for five to six days, then clean the stones and barrel again. Repeat the process for a seven-day run using 400-grit powder. Clean the stones, and remove any broken or cracked ones from the pile.
- Polish the stones
Repeat the tumbling process a final time for seven days, using 1 tablespoon of cerium oxide to create a shine on the stone surfaces.