Dolomitic limestone is a sedimentary carbonate rock composed primarily of calcium magnesium carbonate, chemically represented as CaMg(CO₃)₂, along with varying amounts of calcium carbonate (CaCO₃). It is formed through the geological process of dolomitization, where magnesium-rich fluids partially replace calcium in limestone over millions of years.
Compared to pure calcitic limestone, dolomitic limestone exhibits enhanced hardness, durability, and chemical stability, making it highly valuable across construction, metallurgical, agricultural, and industrial sectors.
Chemical Composition
| Component | Typical Range |
|---|---|
| Calcium Carbonate (CaCO₃) | 55 – 75% |
| Magnesium Carbonate (MgCO₃) | 25 – 45% |
| Silica (SiO₂) | 0.5 – 5% |
| Alumina (Al₂O₃) | Trace – 2% |
| Iron Oxide (Fe₂O₃) | Trace – 1% |
| Organic Matter | Trace |
The elevated MgCO₃ content distinguishes dolomitic limestone from high-calcium limestone.
Physical Properties
| Property | Typical Value |
|---|---|
| Density | 2.7 – 2.9 g/cm³ |
| Porosity | Low – Moderate (5 – 15%) |
| Color | Grey, buff, light brown |
| Texture | Crystalline to granular |
| Mohs Hardness | 3.5 – 4 |
| Water Absorption | Low |
| Decomposition Temperature | 700 – 900 °C (two-stage) |
| Solubility | Lower than pure limestone |
Mechanical Properties
| Property | Typical Range |
|---|---|
| Compressive Strength | 100 – 300 MPa |
| Tensile Strength | 10 – 25 MPa |
| Abrasion Resistance | High |
| Brittleness | Medium |
| Durability | Excellent |
✔ Stronger and harder than calcitic limestone
✔ Comparable to some low-grade marbles
Strengthening & Metallurgical Behavior
Natural Strength Sources:
• Crystalline dolomite structure
• Tight grain interlocking
Strength Enhancement:
• Thermal recrystallization
• Cement stabilization in aggregates
Naturally resistant to abrasion, weathering, and chemical attack.
Metallurgical Role:
An excellent flux material in steelmaking and ferroalloy production. Thermal decomposition
occurs in stages:
CaMg(CO₃)₂ → CaCO₃ + MgO + CO₂
CaCO₃ → CaO + CO₂
Produces dolomitic lime (CaO·MgO) with superior sulfur and phosphorus removal, high slag fluidity, and excellent refractory compatibility.
Key Characteristics
✔ Higher hardness than calcitic limestone
✔ Improved abrasion resistance
✔ Lower solubility and weathering rate
✔ Dual CaO–MgO chemistry
✔ High refractoriness
✔ Stable thermal performance
Refining & Processing Properties
Quarrying:
• Open-pit quarrying
• Moderate to high blasting energy
• Selective mining to control Mg content
Processing:
• Crushing and screening
• Grinding (powder production)
• Calcination (rotary or shaft kilns)
• Hydration (dolomitic lime)
• Agglomeration (pellets, briquettes)
Thermal Processing:
Requires tighter control than calcitic limestone. Produces dead-burned dolomite and
sintered dolomite for refractory applications.
Available Forms
• Raw stone blocks
• Crushed aggregates
• Ground dolomitic limestone
• Dolomitic lime (CaO·MgO)
• Hydrated dolomitic lime
• Pellets and briquettes
• Sintered dolomite
Applications
Construction & Infrastructure:
• Road base and aggregates
• Concrete and asphalt
• Dimension stone
Metallurgical & Industrial:
• Steelmaking flux
• Ferroalloy production
• Refractory bricks
• Glass manufacturing
Agriculture: Soil conditioning and pH correction (supplies Ca & Mg)
Environmental: Water treatment and flue gas desulfurization
Advantages of Dolomitic Limestone
✔ Higher strength than calcitic limestone
✔ Supplies both calcium and magnesium
✔ Superior metallurgical performance
✔ Improved durability and weather resistance
✔ Lower maintenance in construction use
Why Choose Dolomitic Limestone?
Dolomitic limestone is ideal where high strength, abrasion resistance, magnesium chemistry, and thermal stability are required. It offers a cost-effective alternative to pure dolomite while delivering excellent performance across construction, metallurgy, and agriculture.
Quick Comparison
| Feature | Calcitic Limestone | Dolomitic Limestone | Dolomite |
|---|---|---|---|
| MgCO₃ Content | <5% | 25 – 45% | ~45% |
| Strength | Medium | High | Very High |
| Metallurgical Value | Moderate | High | Very High |
| Weather Resistance | Moderate | High | Very High |