sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness of 3 on the Mohs scale, color typically gray, white, or tan, dull to earthy luster, massive or fine-grained crystal structure, good cleavage in three directions (rhombohedral), specific gravity around 2.7.

Identified July 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and compaction of organic remains such as shells, coral, and algal debris, or through the chemical precipitation of calcium carbonate from water in shallow marine environments over millions of years.

Uses & applications

Extensively used in construction as building stone, as an aggregate for road bases, in the manufacturing of cement and lime, in agriculture to neutralize acidic soils, and as a chemical feedstock.

Geological facts

Limestone often contains fossils of ancient marine organisms, providing key insights into Earth's paleontological history. Famous structures like the Great Pyramid of Giza are partially built from limestone.

Field identification & locations

Can be easily identified in the field by its characteristic effervescence (fizzing) when a drop of weak hydrochloric acid or vinegar is applied due to the release of carbon dioxide gas. Found worldwide in sedimentary basins.