Bentonite vs Dolomite — Key Differences, Uses, and When to Choose Each

Introduction

Bentonite and dolomite are both mined mineral products sold as powders and granules, and both are used in agriculture and industry — which is exactly why buyers sometimes confuse them. In reality they are completely different minerals with different chemistry and different jobs. This guide lays out the differences clearly so you order the right one.

They Are Different Minerals

• Bentonite is a clay, composed mainly of montmorillonite (an aluminium silicate). Its defining trait is that it swells and absorbs water, forming viscous, sticky, binding suspensions.
• Dolomite is a calcium-magnesium carbonate (CaMg(CO₃)₂). Its defining trait is that it neutralises acidity and supplies calcium and magnesium. It does not swell.

That fundamental difference — a swelling silicate clay versus an acid-neutralising carbonate — drives everything else.

Side-by-Side Comparison

| Property | Bentonite | Dolomite | |----------|-----------|----------| | Mineral type | Clay (montmorillonite) | Carbonate (CaMg(CO₃)₂) | | Swells in water? | Yes, strongly | No | | Key chemistry | Aluminium silicate | ~28–32% CaO, ~18–22% MgO | | Effect on soil pH | Roughly neutral to alkaline; conditions soil | Raises pH (neutralises acidity) | | Main talents | Binding, swelling, sealing, adsorption | Acid neutralising, Ca/Mg nutrition | | Typical industrial use | Drilling, foundry, civil, litter | Glass, ceramics, steel flux, fillers | | Typical agricultural use | Soil conditioning, fertilizer binder, water retention | Liming, Mg correction, Ca/Mg nutrition |

When to Choose Bentonite

Choose bentonite when the job needs binding, swelling, sealing, water retention, or adsorption:

• Drilling mud and civil slurry/grouting (swelling, filter cake).
• Foundry green-sand binder and iron-ore pelletizing (binding).
• Cat litter (clumping) and industrial absorbents (adsorption).
• In agriculture: conditioning sandy soils to hold water and nutrients, and binding fertilizer granules — see our guide.