sedimentary

Limestone

Calcium Carbonate (CaCO3)

Mohs hardness of 3, light beige to tan or brown in color, earthy or dull luster, fine-grained matrix, vigorous reaction (fizzing) with dilute hydrochloric acid, specific gravity around 2.5-2.7

Identified July 22, 2026More sedimentary →

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Physical properties

Mohs hardness of 3, light beige to tan or brown in color, earthy or dull luster, fine-grained matrix, vigorous reaction (fizzing) with dilute hydrochloric acid, specific gravity around 2.5-2.7

Formation & geological history

Formed through the accumulation and compaction of organic debris like shells, coral, and algal remains, or by chemical precipitation of calcium carbonate in shallow, warm ocean waters.

Uses & applications

Widely used as aggregate in construction, raw material for cement, soil lime in agriculture, dimension stone for architecture, and as an industrial chemical feedback.

Geological facts

Limestone composes about 10% of total sedimentary rock volume on Earth and is famously the primary component of many cave formations like stalactites and stalagmites.

Field identification & locations

Easily identified by its softness (scratched by a copper penny or steel nail) and effervescence with acid; found abundantly worldwide in sedimentary basins.