How to Tumble Rocks: A Beginner's Guide
Quick answer: To tumble rocks, fill a rotary tumbler barrel about two-thirds full of hard rough stone like agate or jasper. Add coarse grit and water, and run it for about a week. Then rinse and repeat with medium grit, fine grit, and polish. The full process takes 3 to 5 weeks and turns rough rock into smooth, glossy stones.
We're rockhounds who mine our own Summerville crazy lace agate in Trion, Georgia, and a lot of it ends up in tumblers. Here's the step-by-step process we recommend for beginners.
What you need
- A rotary rock tumbler: a 2 to 3 lb barrel is a good starting size.
- Rough rock: hard stones of Mohs 6 to 7, such as Summerville crazy lace agate rough.
- Grit: four stages, coarse (60/90), medium (120/220), fine (500), and polish (aluminum oxide or cerium oxide).
- Water, a strainer, and a bucket for rinsing.
Step 1: Pick the right rocks
Use stones that are all about the same hardness, so soft ones don't get ground away by hard ones. Agate, jasper, and quartz (Mohs 6.5 to 7) are the easiest to work with. Mix sizes from about half an inch to two inches, so the stones cushion each other as they tumble.
Step 2: Coarse grind (about 7 days)
Fill the barrel two-thirds to three-quarters full with rock. Add about 2 tablespoons of coarse grit per pound of rock and enough water to just cover the stones. Seal the barrel and run it around the clock for about a week. This stage rounds off the sharp edges and does most of the shaping.
Step 3: Medium grind (about 7 days)
Rinse the rocks and barrel completely. Never pour grit slurry down a sink drain, because it can clog your pipes. Add medium grit and fresh water, and run for another week to smooth out the scratches left by the coarse grit.
Step 4: Fine grind (about 7 days)
Rinse again and repeat with fine grit. After this stage, the stones should look smooth and matte when dry.
Step 5: Polish (about 7 days)
Clean everything carefully, because even a speck of leftover grit can scratch the finish. Add polish and water and run for a final week. Many tumblers add a burnishing step afterward: a day of tumbling with a little soap and water to bring out the shine.
Beginner tips
- Don't rush the coarse stage. If stones still have pits or sharp edges, run coarse again before moving on.
- Keep stages clean. Rinse well between every grit change.
- Add filler such as ceramic media if your barrel is under half full.
- Check weekly for pressure buildup or leaks.
Frequently asked questions
How long does it take to tumble rocks?
About 3 to 5 weeks with a rotary tumbler: roughly one week for each of the four grit stages.
What are the best rocks for tumbling?
Agate, jasper, and quartz. They're hard (Mohs 6.5 to 7), easy to find, and take a high polish. Summerville crazy lace agate from Georgia is a favorite because of its swirling, lace-like bands.
Can you tumble rocks you find outside?
Yes. Pick hard, non-porous stones without cracks. A quick test: if a steel knife won't scratch the rock, it's probably hard enough.
Why are my tumbled rocks not shiny?
Usually the earlier grits didn't fully remove the scratches, or grit got carried into the polish stage. Repeat the fine stage, clean everything thoroughly, and polish again.
What can you make with tumbled stones?
Wire-wrapped jewelry, keychains, display pieces, garden accents, and gifts.
