sedimentary

Limestone

Sedimentary rock composed mainly of calcite (CaCO3)

Mohs hardness: 3; Color: Buff, tan, cream, with iron oxide staining; Luster: Dull, earthy; Texture: Fine-grained, microcrystalline to porous; Effervesces (fizzes) strongly in dilute hydrochloric acid.

Hardness: 3
Color: Buff, tan, cream, with iron oxide staining
Luster: Dull, earthy

Identified July 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in shallow, warm marine or lacustrine environments from the accumulation and compaction of chemical precipitates or organic marine debris such as shell fragments and corals.

Uses & applications

Widely used as building stone, crushed aggregate for construction, raw material for cement, lime manufacture, soil conditioner in agriculture, and dimension stone for landscaping.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Over geological time, soluble limestone landscapes often develop dramatic karst topography, including caves, sinkholes, and underground drainage systems.

Field identification & locations

Identified by its light buff/tan color, relatively soft surface (easily scratched by a steel nail), dull earthy texture, and strong effervescence when tested with acid. Commonly found in former shallow sea beds, quarries, and sedimentary basins worldwide.

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