sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on the Mohs scale; Color: White, gray, tan, yellow, or brown; Luster: Dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect in three directions (for pure calcite); Specific gravity: 2.7 to 2.9

Hardness: 3 on the Mohs scale
Color: White, gray, tan, yellow, or brown
Luster: Dull to earthy

Identified July 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of skeletal fragments from marine organisms such as coral, mollusks, 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 the construction industry for crushed stone in road base, production of Portland cement, as a building dimension stone, in agriculture to neutralize acidic soils, and as a chemical feedstock.

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 constructed largely from limestone blocks.

Field identification & locations

Can be easily identified in the field by its characteristic reaction to dilute hydrochloric acid, producing effervescence (fizzing) due to the release of carbon dioxide gas. Found worldwide in sedimentary basins and ancient sea beds.