If you are sourcing industrial minerals, you have probably come across bentonite. Sodium based, calcium based, CAS number – which ones actually matter when you are placing an order? Let's go through a few practical points.
First, the CAS number – to help with your paperwork
The common CAS number for bentonite is 1302-78-9.
For sodium bentonite, you may also see 85049-30-5 (EINECS 285-199-4)
Having these numbers ready when you draft a PO or prepare customs documents saves time and avoids back-and-forth emails.
Appearance: powder color ranges from white and light yellow to grey-green. This mainly depends on the iron content in the ore. White does not always mean better quality – it depends on which specifications you actually need.
Physical properties you can actually compare
Hardness: Mohs 1–2. You can feel the smooth, greasy texture between your fingers.
Swelling volume: A good sodium bentonite can swell to 15–20 times its dry volume in water. This is one of the quickest ways to check quality.
pH: Sodium grades are alkaline, roughly 7.8–9.6. Calcium grades are lower.
Particle size: Very fine powder. The exact mesh size varies by grade and application.
Other properties such as true density, bulk density, specific surface area, and CEC (cation exchange capacity) vary significantly depending on the ore source, purity, and test method. We do not publish fixed numbers here. Instead, we provide the actual COA for each batch.
Chemical properties: sodium vs calcium
Chemical composition varies by source. Typical components include SiO₂, Al₂O₃, Fe₂O₃, MgO, CaO, Na₂O, and K₂O. Sodium bentonite usually has higher Na₂O content.
What decides the type? Exchangeable cations.
If sodium ions make up more than half of the exchangeable cations → sodium bentonite. If calcium dominates → calcium bentonite.
Sodium bentonite hydrates better, disperses well in water, and swells more. Calcium bentonite usually has lower swelling and gelling ability.
CEC is another useful indicator, but the value changes with ore origin and test method. We will give you the real number from your batch's COA.
Three main applications
Drilling mud: sodium bentonite. Typical requirements: fluid loss <15mL/30min, mud cake thickness <1mm.
Foundry sand binder: sodium bentonite as well. Wet strength is usually ≥0.23 MPa.
Cat litter: high-quality sodium bentonite – fast absorbing, tight clumping, low dust.
Not every sodium bentonite works for all three. Drilling grade and cat litter grade differ in swelling, particle size, moisture, and other parameters. We have seen customers try to use cat litter clay for drilling – and fail the fluid loss test. That is not because the clay is bad; it is simply the wrong grade.
What Snowhite Chemical can do for you
Snowhite Chemical Co., Ltd. has been exporting bentonite for years. We work directly with reliable mines and manage quality control closely.
What we offer:
Real COA for each batch – no inflated numbers
Full export documents: MSDS, certificate of origin, packing list, B/L
MOQ from 1 ton – small trial orders are welcome
SGS or third-party inspection accepted – you can test any parameter
Shipment from main ports such as Tianjin, Shanghai, and Qingdao
If you are not sure which grade fits your application, or you need a specific specification, contact us directly. We will send you the actual data sheet and sample report.
Contact Us
Contact SNOWHITE CHEMICAL CO., LTD now to get COA, free samples and the latest quotation.
Email: shirley@snowhitechem.com
Phone: +86-25-56215758
WhatsApp：+86-13776524331
