Industrial Minerals
What it is
Wollastonite is calcium metasilicate with a naturally needle-shaped crystal. Those needles reinforce the way a short fibre does, which is why it became the standard replacement for asbestos in friction materials, and why it stiffens engineering plastics without the cost of glass fibre.
Why buyers specify it
- Acicular particles reinforce — flexural modulus and heat deflection rise together.
- Low moisture absorption and near-zero volatiles, so it behaves in a melt.
- Naturally white and alkaline, which helps corrosion inhibition in primers.
- The recognised non-hazardous substitute for asbestos in friction and sealing products.
Grades we supply
Grade names are ours; the fineness and the duty are what you match against your current material.
| Grade | Aspect ratio | Typical D50 | Usually bought for |
|---|---|---|---|
| XW-HAR | 15:1 – 20:1 | 8 – 15 µm | Engineering plastics, friction |
| XW-MAR | 8:1 – 12:1 | 6 – 12 µm | Paint, powder coating |
| XW-Powder | 3:1 – 5:1 | 4 – 8 µm | Ceramic bodies, filler duty |
| XW-Surface | 15:1 – 20:1 | 8 – 15 µm | Silane-treated for polyamide |
Other finenesses and surface treatments are available against a firm enquiry. If you are switching from another supplier, send their data sheet and we will match the curve rather than the mesh number.
Typical analysis
Chemistry
| Component | Typical range | Note |
|---|---|---|
| CaO | 44 – 48 % | Theoretical 48.3 % |
| SiO2 | 49 – 53 % | Theoretical 51.7 % |
| Fe2O3 | 0.2 – 0.8 % | — |
| Al2O3 | 0.3 – 1.5 % | — |
| Loss on ignition | 0.5 – 2.5 % | Very low volatiles |
Physical properties
| Property | Typical range | Method basis |
|---|---|---|
| ISO brightness | 85 – 93 % | Elrepho |
| Specific gravity | 2.85 – 2.95 | — |
| pH (10 % slurry) | 9.0 – 10.0 | Alkaline — aids flash rust control |
| Oil absorption | 20 – 30 g/100 g | Low, so high loadings are possible |
| Moisture as packed | ≤ 0.5 % | — |
| Mohs hardness | 4.5 | — |
These are typical ranges for wollastonite, not a specification. The values that govern your order are the ones measured on your lot and printed on its mill test certificate. Ask for a sample and the certificate that goes with it before you commit a production trial.
Where it is used
Wollastonite is not one product sold 4 ways — it is 4 different conversations about the same mineral. We supply it into plastics & masterbatch, paint & coatings, ceramics & sanitaryware and adhesives & sealants, and in each of those the grade that works is chosen for a different reason: fineness in one, brightness in another, oil absorption or purity in the next.
Each industry below has its own page on this site, written for the people who formulate in it rather than for a general reader. If you work in one of them, start there — it will tell you which wollastonite grade we would quote for your application and what we need to know before quoting it.
- Plastics & Masterbatch — Reinforcement in polyamide, polypropylene and thermosets.
- Paint & Coatings — Anti-corrosive primers, powder coatings, matting with reinforcement.
- Ceramics & Sanitaryware — Fast-fire bodies and glazes; lowers firing shrinkage.
- Adhesives & Sealants — Reinforcing filler in construction sealants.
Surface treatment. For polyamide and other polar polymers, a silane-treated grade usually returns its premium in mechanical performance. Tell us the resin and we will recommend the treatment rather than selling the untreated grade and letting you discover the difference.
Packing
| Pack | Detail | Suits |
|---|---|---|
| 25 kg paper or PP bag | Palletised 40 bags per pallet, stretch-wrapped | Powders |
| 50 lb bag | US-standard weight where the plant prefers it | Powders |
| 1,000 kg / 1 MT jumbo bag | Four-loop FIBC with discharge spout | Powders, sand, granules |
| Bulk | Pneumatic tanker or loose in container, where volume justifies it | Sand, granules, lump |
Private-label bags with your own artwork are available from one container. How private label works.
Documents with every shipment
- Mill test certificate for the lot, with the measured values, not the range
- Certificate of analysis signed by the processing plant
- Safety data sheet in the US 16-section GHS format
- Certificate of origin and the commercial invoice and packing list
- Asbestos test report where the mineral and the application call for one
Related minerals
Need a price on wollastonite?
Send the grade, the tonnage and the delivery ZIP code. Quote and free sample back within one business day.