Grinding media that adds no iron to the batch
Flint Pebbles
Naturally rounded high-silica flint, washed and screened into mill charges. The non-metallic grinding medium for ceramic bodies, glazes, frits and pigments — anywhere iron pickup would show in the fired or finished colour.
- Manufactured to: Graded to customer specification
Overview
The reason to grind with stone rather than steel is contamination. Steel media shed iron into the charge, and in a white ceramic body or a pale glaze that iron reappears after firing as specks and as an overall shift in tone. Flint is chemically inert against the batch, so what comes out of the mill is what went in, minus the particle size.
The honest comparison is with alumina, not with steel. Alumina media are denser — about 3.6 against flint's 2.6 — so they grind faster and wear more slowly, and for a high-throughput line they are usually the better economics despite costing several times more per tonne. Flint earns its place on shorter runs, on colour-critical batches, and wherever the mill is already sized around it.
Shape is a specification, not an aesthetic. Sea- and river-tumbled pebbles are rounded through their whole volume, so they wear down evenly and stay round. Crushed material sold as pebbles has fractured faces that chip in the mill, which puts angular fragments into the batch and drops the effective charge weight long before the nominal wear life is up.
A mill is charged with a blend of sizes rather than one, so the large pebbles do the breaking and the small ones do the fine grinding. Tell us the mill volume and what you are milling and we will quote the blend; a single-size charge is almost never the right answer.
Packing options
- Jumbo bag (FIBC)1,000 kg / 1,250 kg
The usual format for a mill recharge
- Woven bag25 kg / 50 kg
Small mills, laboratories and landscape quantities
- Bulk—
Container or tipper, for continuous replenishment contracts
Available gradations
Flint Pebbles
| Size | Typical use |
|---|---|
| Fine charge20 – 30 mm | Final grinding stage, glazes and engobes |
| Medium charge30 – 50 mm | The bulk of most ceramic body and frit charges |
| Coarse charge50 – 80 mm | Primary breaking in large-diameter mills |
- Size
- Fine charge20 – 30 mm
- Typical use
- Final grinding stage, glazes and engobes
- Size
- Medium charge30 – 50 mm
- Typical use
- The bulk of most ceramic body and frit charges
- Size
- Coarse charge50 – 80 mm
- Typical use
- Primary breaking in large-diameter mills
Other cuts can be produced to specification — send us the effective size and uniformity coefficient you need.
Technical specification
| Property | Typical value | Test method |
|---|---|---|
| Silica (SiO₂) | ≥ 98% | XRF |
| Iron oxide (Fe₂O₃) | ≤ 0.15% | XRF |
| Mohs hardness | 7 | — |
| Specific gravity | 2.6 | ASTM C128 |
| Loose bulk density | ≈ 1.55 t/m³ | — |
| Water absorption | ≤ 0.3% | — |
| Shape | Naturally tumbled and rounded — no crushed or fractured faces | — |
| Colour | White to honey and pale grey | — |
- Property
- Silica (SiO₂)
- Typical value
- ≥ 98%
- Test method
- XRF
- Property
- Iron oxide (Fe₂O₃)
- Typical value
- ≤ 0.15%
- Test method
- XRF
- Property
- Mohs hardness
- Typical value
- 7
- Test method
- —
- Property
- Specific gravity
- Typical value
- 2.6
- Test method
- ASTM C128
- Property
- Loose bulk density
- Typical value
- ≈ 1.55 t/m³
- Test method
- —
- Property
- Water absorption
- Typical value
- ≤ 0.3%
- Test method
- —
- Property
- Shape
- Typical value
- Naturally tumbled and rounded — no crushed or fractured faces
- Test method
- —
- Property
- Colour
- Typical value
- White to honey and pale grey
- Test method
- —
Typical values. The certificate issued with your shipment reports the figures measured on that production lot.
Documents
Manufactured to
- Graded to customer specification
Need this grade?
Send the gradation, the volume and the destination port. Our technical team responds within one working day with pricing, lead time and a specimen certificate of analysis.