sedimentary

Limestone

Calcite rock (CaCO3)

Hardness: 3 on Mohs scale, Color: White, gray, tan, or yellowish, Luster: Dull to earthy, Crystal structure: Microcrystalline or fine-grained, Cleavage: None (massive), Specific gravity: 2.7

Identified August 6, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale, Color: White, gray, tan, or yellowish, Luster: Dull to earthy, Crystal structure: Microcrystalline or fine-grained, Cleavage: None (massive), Specific gravity: 2.7

Formation & geological history

Formed through the accumulation of skeletal fragments from marine organisms like coral, algal, and foraminifera, as well as the chemical precipitation of calcium carbonate from water. Typically formed in shallow, warm marine environments over millions of years.

Uses & applications

Used widely in construction (aggregate for concrete, road base), manufacturing of cement, lime production, agriculture (soil conditioning), and metallurgical flux.

Geological facts

Limestone often contains fossils of ancient sea life, providing valuable clues about Earth's history and past climates. Famous structures like the Great Pyramids of Giza were built using limestone blocks.

Field identification & locations

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