sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on the Mohs scale, Color: Tan, beige, white, or gray, Luster: Earthy to dull, Crystal Structure: Trigonal (calcite), Cleavage: Perfect in three directions (rhombohedral), Specific Gravity: 2.71

Identified August 1, 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

Formation & geological history

Formed by the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, as well as the precipitation of calcium carbonate from water. Geological age spans from the Precambrian to recent, often found in shallow marine environments.

Uses & applications

Widely used in the manufacture of cement, as a building material, as aggregate for road bases, in agriculture to neutralize acidic soil, and in the production of lime and glass.

Geological facts

Limestone frequently contains well-preserved fossils of ancient marine life. Famous architectural structures like the Great Pyramid of Giza and parts of the Empire State Building utilize limestone.

Field identification & locations

Easily identified by its reaction to hydrochloric acid, producing effervescence (bubbling). Found globally in sedimentary basins and ancient sea beds.