sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Light gray to white; Luster: Dull or earthy; Structure: Microcrystalline; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Light gray to white
Luster: Dull or earthy

Identified July 19, 2026More sedimentary →

Explore Limestone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3 on Mohs scale; Color: Light gray to white; Luster: Dull or earthy; Structure: Microcrystalline; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.5-2.7

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also form through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used in construction as an aggregate for road bases, a key ingredient in cement, and as a dimension stone for buildings. It is also used as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. The Great Pyramids of Giza are largely constructed from limestone blocks.

Field identification & locations

Can be identified in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbling) when a drop of diluted hydrochloric acid is applied. Commonly found in ancient sea beds.