sedimentary

Limestone

Calcium Carbonate (CaCO3)

Mohs hardness of 3, colors range from white, gray, yellow to brown, dull to earthy luster, fine-grained to coarse-grained crystal structure, good cleavage in three directions (rhombohedral), specific gravity around 2.7.

Identified July 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of skeletal fragments from marine organisms like coral, algal, and foraminifera, as well as the chemical precipitation of calcium carbonate from water in shallow marine environments over millions of years.

Uses & applications

Widely used in construction as building stone, a primary component of portland cement, aggregate for road bases, in agriculture to neutralize acidic soils, and in the manufacturing of glass and paper.

Geological facts

Limestone often contains fossils of ancient marine life. Famous structures like the Great Pyramid of Giza and parts of the Empire State Building utilize limestone in their construction.

Field identification & locations

Easily identified in the field by its characteristic effervescence (fizzing) when a drop of weak hydrochloric acid or vinegar is applied due to the release of carbon dioxide gas. Found worldwide in sedimentary basins.