sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Gray, tan, white, or buff; Luster: Dull to earthy; Structure: Clastic or crystalline; Reaction: Effervesces with dilute acid.

Hardness: 3 on Mohs scale
Color: Gray, tan, white, or buff
Luster: Dull to earthy

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray, tan, white, or buff; Luster: Dull to earthy; Structure: Clastic or crystalline; Reaction: Effervesces with dilute acid.

Formation & geological history

Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. It is also formed by the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Widely used as an architectural stone, in concrete production, as a road base, and in the manufacture of lime. Also used as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains abundant fossils of ancient marine life such as crinoids, brachiopods, and corals.

Field identification & locations

Identify in the field by its soft texture and positive reaction to acid. Often found in layered outcrops near ancient seabeds or quarries. Look for small shell fragments or grain-like textures.