sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale), Color: White to light grey, Luster: Dull to earthy, Texture: Fine-grained, Cleavage: None (conchoidal fracture), Specific Gravity: 2.3-2.7

Identified July 12, 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 (Mohs scale), Color: White to light grey, Luster: Dull to earthy, Texture: Fine-grained, Cleavage: None (conchoidal fracture), Specific Gravity: 2.3-2.7

Formation & geological history

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

Uses & applications

Used extensively in construction as road base, railroad ballast, and an ingredient in cement. Also used as a soil conditioner and in the production of lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes, where it dissolves to form caves and sinkholes.

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 dilute hydrochloric acid or vinegar is applied. Commonly found in areas that were once prehistoric seafloors.