Select Stones by Hardness Compatibility
30 minutesChoose agate, jasper, quartz, or petrified wood of similar Mohs hardness; reject fractured or porous stones.
Field context
This workflow is part of 4 niche fields
Complete guide for rock tumbling project — step-by-step workflow, tools, checklist, and expert tips to get started.
Choose agate, jasper, quartz, or petrified wood of similar Mohs hardness; reject fractured or porous stones.
Fill barrel ⅔ full with stones, add grit per manufacturer ratio, cover with water; tumble 7–10 days checking daily seal.
Rinse stones and barrel thoroughly between stages; run 220 grit (7 days), 600 grit (7 days), polish compound (7 days).
Examine under bright light for remaining scratches; re-run failed stones in fresh batch; store polished stones dry in divided tray.
Track tumbling duration for each grit stage to prevent over-tumbling that rounds stones to ovals.
Verify all stones in batch share compatible Mohs hardness before loading barrel to prevent soft stone destruction.
Estimate stone porosity to predict grit retention in fractured specimens and adjust stage duration.
Convert hardness values when mixing commercial grit recommendations with mineral hardness data.
Standard grit progression for agate and jasper (rotary tumbler).
| Stage | Grit | Duration | Fill Level |
|---|---|---|---|
| 1 — Coarse | 60/90 silicon carbide | 7–10 days | ⅔ barrel + water |
| 2 — Medium | 220 silicon carbide | 7 days | Rinse completely |
| 3 — Fine | 600 silicon carbide | 7 days | Rinse completely |
| 4 — Polish | TXP or cerium oxide | 7 days | Add burnishing if dull |
One soft stone in hard batch becomes mud — sort ruthlessly before loading.
Obsessive rinsing between grits separates success from scratched polish.
Open barrel only in sink — silicon carbide slurry stains permanently.