sedimentary

Limestone

Calcium carbonate (CaCO3)

Hardness of 3 on the Mohs scale, color typically ranges from white, gray, yellow to brown, dull to earthy luster, fine-grained to coarse crystalline structure, good cleavage in three directions (rhombohedral for calcite). Specific gravity is around 2.7.

Identified August 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and compaction of organic remains such as shells, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water in marine environments. Ages range from Precambrian to modern times.

Uses & applications

Widely used in the construction industry as a building material, crushed stone for road base, an ingredient in the manufacture of Portland cement, agricultural lime for soil conditioning, and in the production of glass and paper.

Geological facts

Limestone often contains fossils of ancient marine organisms, providing a rich record of Earth's history. Famous geological formations like the white cliffs of Dover are composed largely of chalk, a soft variety of limestone.

Field identification & locations

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