sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale. Color ranges from white, gray, yellow, to brown. Luster: earthy to sub-vitreous. Crystal structure: trigonal (calcite). Cleavage: perfect in three directions. Specific gravity: 2.7 to 2.9.

Hardness: 3 on the Mohs scale
Luster: earthy to sub-vitreous

Identified August 6, 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 through the accumulation of skeletal fragments from marine organisms such as coral, algal, and foraminifera, or through the chemical precipitation of calcium carbonate from water. Typically forms in shallow marine environments over millions of years.

Uses & applications

Extensively used in construction as a building material, as an aggregate for road bases, as an ingredient in Portland cement, in agriculture to neutralize acidic soils, and in the manufacture of glass and paper.

Geological facts

Limestone often contains well-preserved fossils of ancient marine life. Famous structures built with limestone include the Great Pyramid of Giza and the Empire State Building.

Field identification & locations

Can be easily identified in the field by its characteristic fizzing or effervescence when a drop of dilute hydrochloric acid is applied due to the release of carbon dioxide gas. Found worldwide in sedimentary basins.