Limestone

By tonnage the most quarried rock on earth, mostly because cement is made by roasting it: heating calcium carbonate above 900 °C drives off carbon dioxide to leave quicklime, and that reaction is itself about half of the cement industry's emissions. As building stone it is soft, easily carved, and slowly dissolved by acid rain, which is why medieval limestone carvings lose their faces. The density band is wide because porosity varies enormously between a chalky and a compact limestone.

Properties

Density

2,450 kg/m³ (2,000–2,700) — 2.45 g/cm³

Tensile strength

3–10 MPa

Young's modulus

40 GPa

Thermal conductivity

1.3 W/(m·K)

Hardness

3 Mohs

Thermal expansion

8 µm/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• Cement and lime manufacture
• Building stone and cladding
• Aggregate and road base
• Agricultural lime and flue gas desulfurization

How it compares

Does it rust?

Limestone contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

Is it magnetic?

Limestone is not a metal and has no ferromagnetic response.