Industrial Minerals
What it is
Bentonite is a clay dominated by montmorillonite, which swells to many times its dry volume in water. That swelling is the product: it binds foundry sand, seals a borehole wall and holds solids in suspension in a drilling fluid.
Why buyers specify it
- Sodium grades swell strongly for sealing and viscosity; calcium grades bond without the swell.
- High green and dry compression strength in moulding sand, with low burn-out.
- Thixotropic — stiff at rest, fluid when sheared, which is exactly what a drilling mud needs.
- Naturally occurring and inexpensive relative to synthetic rheology additives.
Grades we supply
Grade names are ours; the fineness and the duty are what you match against your current material.
| Grade | Type | Key figure | Usually bought for |
|---|---|---|---|
| XN-Foundry | Sodium-activated | Green strength 170–200 kPa | Green sand moulding |
| XN-API | Sodium | Yield ≥ 90 bbl/tonne | Water-based drilling fluids |
| XN-Civil | Sodium | Swell index 24–30 mL/2 g | Slurry walls, pond sealing |
| XN-Bleach | Acid-activated | Bleaching power 85–95 % | Edible oil refining |
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 |
|---|---|---|
| SiO2 | 55 – 65 % | — |
| Al2O3 | 17 – 22 % | — |
| Fe2O3 | 3 – 6 % | Typical of Kutch bentonite |
| MgO | 2 – 4 % | — |
| Na2O | 1.8 – 3.0 % | Sodium grades |
| Loss on ignition | 6 – 12 % | — |
Physical properties
| Property | Typical range | Method basis |
|---|---|---|
| Swell index | 18 – 30 mL / 2 g | Free swell in water |
| Moisture as packed | 8 – 12 % | — |
| Residue on 200 mesh | ≤ 5 % | Wet sieve |
| pH (5 % slurry) | 8.5 – 10.0 | — |
| Montmorillonite content | 75 – 90 % | Methylene blue |
These are typical ranges for bentonite, 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
Bentonite is not one product sold 3 ways — it is 3 different conversations about the same mineral. We supply it into foundry & refractories, oil & gas drilling and ceramics & sanitaryware, 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 bentonite grade we would quote for your application and what we need to know before quoting it.
- Foundry & Refractories — Green sand bond; the property that holds the mould together before pouring.
- Oil & Gas Drilling — Viscosifier and filtration-control agent in water-based mud.
- Ceramics & Sanitaryware — Small additions raise plasticity and suspend a slip.
API grades are a different product. API 13A bentonite for drilling must meet yield and filtrate limits that a civil or foundry grade will not pass. Specify the end use on the enquiry so we quote the right one rather than the cheapest one.
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 bentonite?
Send the grade, the tonnage and the delivery ZIP code. Quote and free sample back within one business day.