sedimentary

Limestone

Calcium carbonate rock (CaCO3)

Hardness: 3 on Mohs scale; Color: typically light gray, tan, white, or yellowish; Luster: earthy to sub-vitreous; Crystal structure: microcrystalline or fine-grained; Cleavage: none distinct; Specific gravity: 2.7 - 2.9

Hardness: 3 on Mohs scale
Color: typically light gray, tan, white, or yellowish
Luster: earthy to sub-vitreous

Identified August 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, or through the chemical precipitation of calcium carbonate from water. Deposited in shallow marine environments over millions of years.

Uses & applications

Widely used in construction as building stone, a primary component of Portland cement, crushed stone for road base, agricultural lime to neutralize soil acidity, and in the production of glass and steel.

Geological facts

Limestone is famous for forming spectacular karst landscapes, including underground caves, stalactites, and stalagmites. Many of the world's most famous monuments, including the Great Pyramid of Giza, are built from limestone.

Field identification & locations

Easily identified by its characteristic fizz when a weak acid like vinegar (acetic acid) is applied, due to the release of carbon dioxide gas. Found worldwide in sedimentary basins and ancient sea beds.