sedimentary

Limestone

Calcium Carbonate (CaCO3)

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

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

Identified August 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed mainly from the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, typically in shallow, warm marine waters over millions of years.

Uses & applications

Widely used in the construction industry for crushed stone in road base, as an aggregate for concrete, as a main component of Portland cement, and in agriculture for soil conditioning.

Geological facts

Limestone formations often contain well-preserved fossils and can dissolve slightly in acidic water, creating extensive cave systems, sinkholes, and karst topography.

Field identification & locations

Easily identified by its characteristic fizz when a drop of dilute hydrochloric acid is applied, due to the release of carbon dioxide gas. Found worldwide in sedimentary basins.