sedimentary

Limestone

Calcareous sedimentary rock (CaCO3)

Hardness: 3 on Mohs scale; Color: typically white, gray, tan, or yellowish; Luster: dull to earthy; Crystal structure: microcrystalline or fine-grained; Cleavage: none (conchoidal fracture); Specific gravity: 2.7

Hardness: 3 on Mohs scale
Color: typically white, gray, tan, or yellowish
Luster: dull to earthy

Identified July 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of skeletal fragments from marine organisms like coral, mollusks, and foraminifera, or through the chemical precipitation of calcium carbonate from water in marine and lacustrine environments.

Uses & applications

Widely used in construction as building stone, a primary component of Portland cement, crushed stone for road bases, soil conditioning in agriculture, and in the manufacture of glass and paper.

Geological facts

Limestone formations often host extensive cave systems due to the dissolution of calcium carbonate by slightly acidic groundwater over thousands of years.

Field identification & locations

Can be easily identified in the field by its characteristic reaction to dilute hydrochloric acid, producing effervescence (bubbling) due to the release of carbon dioxide.