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In a rotary tumbler, hard stones like agate, jasper and quartz take about 4 to 8 weeks: roughly a week per stage, with the coarse grind often running two weeks or more. Softer stones finish sooner because they grind faster. A vibratory tumbler polishes already-shaped stones in about 1 to 2 weeks.
So how long does a rock tumbler take for your stones? The single biggest variable is Mohs hardness. Most published schedules, including the familiar "one week per grit," were written for stones around Mohs 7. The calculator below adjusts each stage for your stone, your tumbler, and how rough your starting material is.
Rock tumbling timeline calculator
Pick your stone or its Mohs hardness, your tumbler and how rough the stones are. You get days per stage, a total and when to make the first check.
Sources: Mohs 7 rotary schedules from the Lortone, Harbor Freight and Kingsley North tumbler manuals. Coarse-time adjustment (about 1.5 fewer days per Mohs point below 7), hardness values, the obsidian recipe and the vibratory schedule from Rocktumbler.com. Results are starting points: a stage is done when the stones pass its check.
How the Calculator Works
Pick three things and the calculator returns days per stage and a total:
- Your stone (or its Mohs hardness). The calculator pulls hardness from a reference list, such as agate at 7 or obsidian at 5 to 6.
- Your tumbler type: rotary, vibratory, or rotary coarse with vibratory finishing.
- Your starting shape: angular rough, partly rounded rough, or smooth pebbles such as beach stones.
It starts from manufacturer schedules for Mohs 7 stones, then shortens the coarse stage for softer material using Rocktumbler.com's rule of thumb: reduce coarse time by about 1.5 days for each Mohs point below 7. Angular rough adds coarse time; smooth pebbles reduce it. Every result is a starting point. A stage is done when the stones look done, so the calculator also tells you when to make your first check.
How Long Does a Rock Tumbler Take? Rotary Timeline for Hard Stones (Mohs 7)
This is the baseline: agate, jasper, quartz, petrified wood, chert, aventurine and tiger's-eye, all about 7 on the Mohs scale per Rocktumbler.com.
| Stage | Grit | Typical days | First check | Sources |
|---|---|---|---|---|
| 1. Coarse | 60/90 silicon carbide | 7 to 10, often 14 or more | After 24 hours (vent), then every few days | Kingsley North, Harbor Freight, Rocktumbler.com |
| 2. Medium | 120/220 or 150/220 | About 7 (plus 2 to 3 if needed) | Day 2 to 3 | Kingsley North, Harbor Freight |
| 3. Pre-polish | 500 to 600 | About 7 | Every other day | Kingsley North, Harbor Freight |
| 4. Polish | Aluminum oxide, cerium oxide or tin oxide | 5 to 7 | Day 5 | Kingsley North, Harbor Freight |
| 5. Burnish (optional) | Powdered soap | At least 4 | Day 4 | Kingsley North, Harbor Freight |
| Total | About 4 to 8 weeks | Rocktumbler.com; Harbor Freight says 4 to 6 |
Lortone's manuals take a simpler line: check after 2 to 3 days, and expect each stage to end after 5 to 7 days. That's a good rule if you inspect diligently.
Why the wide range on coarse? Rocktumbler.com says its own team usually runs coarse for at least two weeks, and sometimes up to a month for large pieces with awkward shapes. Kingsley North calls coarse the most important step and says to repeat it with fresh grit if stones aren't evenly rounded. Most "my stones didn't polish" complaints trace back to a rushed coarse stage.
How Hardness Changes the Timeline
Grit wears rock down by scratching it, so softer stones lose material faster. Rocktumbler.com gives these coarse-stage starting points:
| Mohs hardness | Example stones | Coarse stage starting point |
|---|---|---|
| 7 | Agate, jasper, quartz, petrified wood, tiger's-eye | At least 7 days, often 14 or more |
| 6 to 7 | Unakite, labradorite, amazonite, granite | About 5.5 to 7 days |
| 6 | Rhodonite, opal (5.5 to 6.5) | About 5.5 days |
| 5 to 6 | Sodalite, turquoise, lapis lazuli, obsidian | About 4 to 5.5 days, or skip coarse (see below) |
| 4 | Fluorite | About 4 to 5 days |
| 3 to 4 | Calcite, marble, malachite, rhodochrosite | About 2 to 3 days |
These come from Rocktumbler.com's Mohs hardness guidance (about 1.5 fewer days per point below 7) and its examples: calcite and marble may round in 2 to 3 days, and fluorite and obsidian in 4 to 5. Mohs values are from Rocktumbler.com's hardness table.
Mohs hardness scale for rock tumbling
Select a step on the scale, or a stone below, to see which tumbling stones sit there and what that hardness means in the barrel.
Reference minerals: the standard Mohs scale. Tumbling stone hardness values and tumbling notes: Rocktumbler.com's hardness table and tumbling guides.
Special Case: Obsidian and Apache Tears
Obsidian is about Mohs 5 to 6 and fractures easily, and Rocktumbler.com's obsidian recipe skips the coarse grit entirely. It uses three steps instead: medium grit, fine grit, then polish. Its snowflake obsidian page suggests about 10 to 12 days in medium and about 5 days in fine before polishing. Rocktumbler.com also warns that a full week of coarse grit can reduce obsidian, sodalite and glass to tiny particles.
Glass and Sea Glass
Glass falls in the soft group, so treat it like obsidian: short or no coarse runs and close checks. Our upcoming guide to making sea glass in a rock tumbler covers it step by step.
Harder Than 7
Stones harder than quartz, such as beryl (7.5 to 8) and topaz (8), wear down more slowly and need longer in coarse grit, per Rocktumbler.com. Expect extended coarse runs and check progress weekly.
Never Mix Hardness in One Barrel
The timeline only works if everything in the barrel shares a hardness range. Rocktumbler.com's example: by the time agate (7) is shaped, obsidian (5 to 6) in the same barrel would be ground too small. Sort first. Our upcoming guide to the best rocks for tumbling lists stones by hardness.
Vibratory Tumbler Timeline
Vibratory tumblers don't round rough rock well, so they're mostly used on stones that are already shaped. Rocktumbler.com's vibratory schedule:
| Stage | Grit | Typical time |
|---|---|---|
| Medium | 150/220 | 12- to 24-hour runs, washing between runs, until smooth: usually 3 to 7 days |
| Fine (pre-polish) | 500/600 | 2 to 3 days |
| Polish | Aluminum oxide polish | 2 to 3 days |
| Total | About 1 to 2 weeks |
Thumler's says its UV-18 vibratory polishes up to four times faster than rotary tumblers. For a full comparison, see our rotary vs vibratory rock tumbler guide.
Rotary Plus Vibratory: The Fastest Path
Many hobbyists shape in a rotary, then finish in a vibratory:
- Rotary coarse: 1 to 3 weeks until stones are rounded.
- Vibratory medium, fine and polish: about 1 to 2 weeks.
Rocktumbler.com says this combination is about two weeks faster than rotary alone. If you run both machines at once, you can finish a new batch every 1 to 3 weeks.
Worked Examples
These are calculator outputs based on the published ranges above. Your stones will tell you when they're ready.
Agate, angular rough, rotary tumbler
- Coarse: 14 days (two 7-day runs with fresh grit)
- Medium: 7 days
- Pre-polish: 7 days
- Polish: 7 days
- Optional burnish: 4 days
- Total: about 5 to 6 weeks
Jasper beach pebbles, already smooth, rotary tumbler
- Coarse: 7 days (check for pits at day 4)
- Medium: 7 days
- Pre-polish: 7 days
- Polish: 5 to 7 days
- Total: about 4 weeks
Sodalite (Mohs 5.5 to 6), rotary tumbler
- Coarse: about 4.5 to 5.5 days, checking daily after day 3
- Medium: about 7 days, checking at day 2 to 3
- Pre-polish: about 7 days
- Polish: 5 to 7 days
- Total: about 3.5 to 4 weeks
Agate, rotary coarse plus vibratory finish
- Rotary coarse: 14 days
- Vibratory medium: 3 to 7 days
- Vibratory fine: 2 to 3 days
- Vibratory polish: 2 to 3 days
- Total: about 3 to 4 weeks
What Else Changes the Timeline
- Starting shape. Rocktumbler.com notes that rough, angular or ugly starting shapes lengthen the coarse stage. Beach pebbles are often already well on their way.
- How picky you are. Re-running stones that aren't perfect adds days but makes better finished stones.
- Fill level. An underfilled barrel tumbles poorly and chips stones. Lortone recommends filling 1/2 to 2/3 full, and Kingsley North and Harbor Freight allow up to 3/4. Top up with ceramic media or plastic pellets.
- Slurry and water. Too much water cushions the load and slows grinding. Kingsley North says water should just reach the bottom of the top layer of stones.
- Grit dose. Under-dosing slows every stage. Lortone's chart calls for 4 tablespoons of each grinding grit in a 3 lb barrel. See our rock tumbler grit guide.
- Your tumbler. A sturdy, continuous-duty machine keeps a steady pace for weeks. Our best rock tumbler picks focus on machines that can run around the clock.
How to Tell a Stage Is Finished
Time is a guide, but the stones decide.
- Coarse: every stone is rounded, with no sharp edges, pits or cracks you can see. If even a few aren't, repeat with fresh grit.
- Medium: an even, smooth matte surface all over, per Kingsley North's day-7 check.
- Pre-polish: a faint sheen when dry and a silky feel.
- Polish: Kingsley North's test is that a finished stone looks the same wet and dry.
For the full procedure, read our step-by-step guide to rock tumbling.
FAQ
How long does it take to tumble rocks?
In a rotary tumbler, about 4 to 8 weeks for hard stones like agate and jasper, according to Rocktumbler.com, with roughly a week per stage and often two or more weeks of coarse grind. Harbor Freight's manual puts its tumbler's cycle at 4 to 6 weeks. A vibratory tumbler finishes pre-shaped stones in about 1 to 2 weeks.
How long should rocks stay in each stage?
For Mohs 7 stones in a rotary: coarse 7 to 10 days or more, medium about 7 days, pre-polish about 7 days, and polish 5 to 7 days. Lortone's instructions call for 5 to 7 days per stage and a check at 2 to 3 days.
Can you tumble rocks too long?
Yes, especially soft stones in coarse grit. Rocktumbler.com warns that a full week of coarse grit can reduce obsidian, sodalite and glass to tiny particles. Hard stones are more forgiving, but over-running a stage costs grit, power and machine wear.
Why does the first stage take so long?
Coarse grit does all the shaping: removing sharp edges, pits and cracks. Hard, angular rough needs a lot of material removed. Rocktumbler.com says it often runs coarse for at least two weeks and sometimes up to a month for large, awkwardly shaped pieces.
How can I make rock tumbling faster?
Sort stones by hardness, fill the barrel to the recommended level, and inspect often so you move on as soon as a stage is done. The biggest speed-up is finishing in a vibratory tumbler: Rocktumbler.com says rotary coarse plus vibratory finishing is about two weeks faster than rotary alone.