sedimentary

Limestone

Limestone (Calcium Carbonate, CaCO3)

Hardness: 3 on the Mohs scale. Color: Varies widely, commonly white, gray, tan, or yellowish. Luster: Earthy to dull. Crystal structure: Microcrystalline or granular calcite. Cleavage: Good rhombohedral cleavage in pure crystals. Specific gravity: 2.7 to 2.9.

Hardness: 3 on the Mohs scale
Color: Varies widely, commonly white, gray, tan, or yellowish
Luster: Earthy to dull

Identified July 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms mainly in clear, warm, shallow marine waters through the accumulation of shell, coral, algal, and fecal debris, or through the chemical precipitation of calcium carbonate from water.

Uses & applications

Widely used in the construction industry as crushed stone for road base, aggregate in concrete, and as a primary raw material for manufacturing Portland cement and lime.

Geological facts

Limestone often contains fossils of ancient marine organisms since it forms in water bodies. Famous structures like the Great Pyramid of Giza were built largely using limestone blocks.

Field identification & locations

Can be easily identified in the field by applying a drop of dilute hydrochloric acid, which will cause it to fizz vigorously due to the release of carbon dioxide gas. Found globally in sedimentary basins.