sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale; Color: typically white, gray, tan, or yellowish; Luster: earthy to dull; Crystal structure: hexagonal-rhombohedral (as calcite); Cleavage: perfect rhombohedral; Specific gravity: 2.7 - 2.9

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

Identified July 30, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Widely used in the manufacturing of cement, as a building material, in road construction, as an agricultural soil conditioner, and as a chemical feedstock.

Geological facts

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

Field identification & locations

Easily identified by its characteristic reaction to dilute hydrochloric acid, producing effervescence (fizzing) due to the release of carbon dioxide. Found worldwide in sedimentary basins.