sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, color ranges from white, gray, yellow to brown, dull to earthy luster, fine-grained to coarse crystalline structure, excellent cleavage in three directions (rhombohedral for calcite), specific gravity of 2.71.

Identified August 4, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Extensively used in construction as building stone, a primary component of Portland cement, as aggregate for road bases, in agriculture to neutralize acidic soils, and in the production of glass and steel.

Geological facts

Limestone often contains fossils of ancient sea life because of its marine origins. Famous structures like the Great Pyramid of Giza were partially constructed using limestone blocks.

Field identification & locations

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