Choose grinding jar and ball material (agate, zirconia, steel, tungsten carbide, alumina, PTFE) by sample hardness and contamination tolerance.
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Load example grinding media selector data to see the full workflow
Common: quartz 7, soil 6, calcite 3
Ranked candidates
| Rank | Media | Mohs | Density (g/cm³) | Contamination | Cost | Fit score |
|---|---|---|---|---|---|---|
| 1 | Zirconia (YSZ) | 8.5 | 6.05 | Zr, Y | $$$ | 4.8 |
| 2 | Agate | 7 | 2.65 | Si, O | $$$ | 2.3 |
Excluded media
Hardness vs. density — candidate space
Blue = ranked candidates · Dark blue = top pick · Grey = excluded · Red line = sample hardness
When to use
Do not use for
Ball and jar wear together. If you use agate balls in a stainless-steel jar (or vice versa), the jar material introduces contamination independent of the ball selection. For metal-free or ultra-clean work, both balls and jar must be the same material (agate jar + agate balls; zirconia jar + zirconia balls). This selector recommends media only — confirm that your jar material matches.
Agate (Mohs 7) cannot grind quartz sand (Mohs 7) — the margin is zero, and agate will wear. Zirconia (Mohs 8.5) covers quartz and most silicate minerals while staying acceptably clean for trace-element work (Zr/Y instead of Fe/Cr/Ni). If your soil or geological sample contains quartz, the selector will exclude agate and rank zirconia top automatically.
Ball impact energy scales with mass (density × volume). Tungsten carbide (ρ 14.95 g/cm³) delivers roughly 5× the impact energy per ball of agate (ρ 2.65 g/cm³) at the same diameter. For very hard or coarse samples where grinding time is the constraint, higher-density media reduces time at the cost of contamination risk. This scatter chart plots all media on the hardness-vs-density plane so you can visualize the energy-contamination trade-off.
For very soft samples (sugar, talc, polymers — Mohs 1–2), all media types qualify on the hardness rule, and contamination constraint alone governs selection. For hard ceramics and alloys (Mohs 8–9), only tungsten carbide qualifies; the entire rest of the media database is excluded by the hardness rule. Run this selector at both ends of your expected sample hardness range to understand your margin.
Selection algorithm: (1) Hard exclude media where `media.mohs − sample.mohs < 1`. (2) Apply contamination filter: metal-free → agate or PTFE only; Fe-free → exclude stainless/hardened steel; ultra-clean → agate or zirconia only; none → no filter. (3) If wet milling, exclude media where `wetOk = false`. (4) Score remaining candidates: `score = hardnessMargin × 1.0 + density × 0.3 + (4 − costTier) × 0.5`. (5) Sort descending by score. Media data sourced from ASTM-referenced manufacturer density and Mohs values; cost tiers are relative planning categories (1 = cheapest, 4 = most expensive).
Last validated 2026-06-14. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.
ConductScience Grinding Media Selector (v1.0.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/grinding-media-selector
Suryanarayana C. Mechanical alloying and milling. Progress in Materials Science. 2001;46(1–2):1–184. doi:10.1016/S0079-6425(99)00010-9
Burmeister CF, Kwade A. Process engineering with planetary ball mills. Chemical Society Reviews. 2013;42(18):7660–7667. doi:10.1039/c3cs60089c
The single most important principle in media selection is that grinding media must be harder than the sample it grinds. When this relationship is reversed, the sample acts as an abrasive against the softer media, causing preferential media wear that:
This selector enforces the ≥ 1 Mohs margin as a hard rule and moves any media that fails to the "Excluded" list with an explanation.
The primary contamination source in ball milling is media wear — the elements constituting the ball and jar surface are introduced into the sample at the nanogram-to-microgram level per gram of sample, depending on sample hardness, milling energy, and duration.
4 × 50–500 mL pots, down to 0.1 µm, reciprocal timer.
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