sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, typically gray, white, or tan in color, dull to earthy luster, fine-grained to coarse crystalline structure, good cleavage in some forms, specific gravity around 2.7.

Identified July 31, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, typically gray, white, or tan in color, dull to earthy luster, fine-grained to coarse crystalline structure, good cleavage in some forms, specific gravity around 2.7.

Formation & geological history

Formed through the accumulation and compaction of organic remains such as shell, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water in marine environments over millions of years.

Uses & applications

Widely used in construction as building stone, as an aggregate for road bases, in the production of cement and lime, in agriculture to neutralize acidic soils, and in the manufacturing of glass and paper.

Geological facts

Limestone often contains fossils of ancient marine organisms and is the primary rock type that forms caves and karst landscapes through the process of chemical dissolution by acidic groundwater.

Field identification & locations

Easily identified by its reaction with weak hydrochloric acid, which causes it to fizz and release carbon dioxide gas. Commonly found in sedimentary basins and ancient sea beds worldwide.