The rock tumbling handbook
From rough rock to a shine, one grit at a time
Grit by grit: how much to load, how long to run each stage, and what to change when the stones come out dull, scratched or cracked.
How much grit, and for how long?
Chart, dated schedule and log sheet →Your batch
35 to 53 daysstart to shine
Load 1.8 to 2.3 lb of rock (agate, jasper, quartz, petrified wood), barrel 1/2 to 3/4 full, water just below the top layer.
- 1
60/90 silicon carbide
about 4 tablespoons · 7 days per run; often 2 to 4 runs
- 2
150/220 silicon carbide
about 4 tablespoons · about 7 days
- 3
500 or 600 silicon carbide
about 4 tablespoons · about 7 days
- 4
aluminum oxide or cerium oxide polish
about 4 tablespoons · 7 to 10 days
- 5
plain soap, no grit
about 1 tablespoon of grated bar soap · 1 hour to 1 day
Amounts follow the common rule of two level tablespoons of grit per pound of rock in a rotary barrel. Your tumbler's manual wins where it differs. Times are typical ranges: the stones decide when a stage is done, not the calendar.
Something went wrong?
Find the symptom, read the cause, change one thing on the next run.
- Tumbled rocks are not shiny after polishNine causes of dull tumbled rocks, matched to what you see on the stone, with the grit step to go back to and the fix for haze, scratches and bruises.
- Rock tumbler barrel is not turningA rock tumbler that will not turn usually has a slipping barrel, an overloaded barrel or a worn belt. 7 causes in checking order, with the fix for each.
- Rock tumbler is too loud or squeakingA rubber-barrel rock tumbler runs at about 55 to 64 dB at three feet. What rattles, hums and squeaks mean, how to oil the bearings and 5 ways to quiet it.
- Slurry leaking from the tumbler barrelA leaking rock tumbler usually has grit on the lid seal, a badly seated lid or gas pressure. 7 causes with fixes, plus how to open a stuck barrel safely.
The process, stage by stage
Four grits and a wash. Each stage only removes the scratches of the one before it, so nothing gets skipped.
- ·Tumbler and setupChoosing a tumbler and keeping it running: barrels, belts, speed and noise.6 notes · 5 gear guides
- ·Rough rockWhich rocks tumble well, where to get them and how hardness decides what goes in one load.7 notes · 1 gear guide
- ·Loading the barrelHow full, how much grit and water, and when to add ceramic media or plastic pellets.3 notes · 4 gear guides
- 1Coarse grindStep 1: shaping the stones with coarse 60/90 silicon carbide grit.3 notes · 1 gear guide
- 2Medium grindStep 2: smoothing with medium 150/220 grit.0 notes · 1 gear guide
- 3Pre-polishStep 3: fine 500 or 600 grit until the stones look satin.0 notes · 1 gear guide
- 4PolishStep 4: aluminum oxide or cerium polish for the shine.1 note · 1 gear guide
- 5Burnish and cleanupSoap burnishing, getting rid of slurry and what to do with finished stones.3 notes · 0 gear guides
Charts to pin above the tumbler
Reference tables with a clean print version.
- Best rocks for tumbling: hardness chart and rocks to avoidHardness chart for 20 common tumbling rocks: Mohs value, whether each one polishes, which rocks can share a barrel and which to skip.Printable
- Rock tumbling grit chart: grit size, amount and time for each stageRock tumbling grit chart for all four steps: grit size, what each step does, days per step and how to tell it is done, plus about 2 tbsp of grit per pound.Printable
- Rock tumbler speed chart: RPM by barrel size and stageRock tumbler speed chart: rpm range for barrel diameters from 3 to 10 inches, published speeds for 6 hobby tumblers, and the dial setting for each stage.Printable
Gear, one item at a time
Narrow guides to a single consumable or tool, compared by what the listings state.
- Best rough rocks for tumbling: mixes and single-stone bags
- Best rock tumblers and grit for making sea glass
- Best rock tumblers for kids: kits by age and barrel size
- Best rock tumblers for adults: hobby-grade rotary machines
- Best plastic pellets for rock tumbling and when to use them
- Best ceramic media for rock tumbling: sizes and how much to buy
- Best grit refills for a National Geographic rock tumbler
- Best rock tumbler grit kits for a full 4-stage run
- Best rock tumbler replacement belts and how to pick the size
- Best rock tumbler replacement barrels and lids by size
- Best rock tumbling polish for step 4
- Best pre-polish grit for rock tumbler step 3
- Best medium grit for rock tumbler step 2
- Best coarse rock tumbler grit: 60/90 silicon carbide for step 1