sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Grey to brownish-grey; Luster: Dull, earthy; Texture: Fine-grained, microcrystalline or clastic; Cleavage: None (conchoidal to irregular fracture).

Hardness: 3 on Mohs scale
Color: Grey to brownish-grey
Luster: Dull, earthy

Identified July 26, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Grey to brownish-grey; Luster: Dull, earthy; Texture: Fine-grained, microcrystalline or clastic; Cleavage: None (conchoidal to irregular fracture).

Formation & geological history

Formed primarily in shallow, warm marine environments through the accumulation and compaction of organic debris such as shell, coral, algal, and fecal debris, or chemical precipitation of calcium carbonate.

Uses & applications

Extensively used in construction as crushed stone, aggregate, building facing, and as a key raw material in cement and lime production.

Geological facts

Limestone reacts with dilute acid (effervesces/fizzes), which is a key diagnostic test. It often contains fossils and is the primary rock type in which karst landscapes and caves develop.

Field identification & locations

Can be identified in the field by its soft nature (scratchable with a steel nail) and visible fizzing when exposed to acid like vinegar. Extremely common globally in sedimentary basins.