sedimentary

Limestone

Calcareous sedimentary rock (CaCO3)

Hardness: 3 on the Mohs scale; Color: Light gray, white, yellowish, or brownish; Luster: Earthy to dull; Crystal structure: Microcrystalline to cryptocrystalline calcite; Cleavage: None (has a conchoidal to uneven fracture); Specific gravity: 2.7 to 2.9

Hardness: 3 on the Mohs scale
Color: Light gray, white, yellowish, or brownish
Luster: Earthy to dull

Identified August 3, 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, or through the chemical precipitation of calcium carbonate from water. Deposited in marine environments over millions of years.

Uses & applications

Extensively used in construction as a building material, an aggregate for roads, a primary ingredient in the manufacture of Portland cement, in agriculture to neutralize acidic soil, and in the production of lime.

Geological facts

Limestone often contains fossils of ancient marine life. Famous architectural structures made from limestone include the Great Pyramid of Giza and the Empire State Building.

Field identification & locations

Can be easily identified in the field by its distinctive gray or light color, softer nature, and a strong fizzing reaction when exposed to dilute hydrochloric acid due to the release of carbon dioxide.