sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs), Color: White, cream, or light grey, Luster: Dull to earthy, Structure: Fine-grained to massive, Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.7

Identified June 29, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs), Color: White, cream, or light grey, Luster: Dull to earthy, Structure: Fine-grained to massive, Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.7

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. Can also form through precipitation from calcium-rich water in caves or hot springs. Geological ages vary from Precambrian to Holocene.

Uses & applications

Extensively used in construction (building stone, concrete aggregate), cement manufacturing, soil neutralized in agriculture, and as a refinery for steel and glass.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Many of the world's most famous caves, including Mammoth Cave in Kentucky, are carved into limestone by acidic water.

Field identification & locations

Identifiable in the field by hissing/fizzing when a drop of diluted hydrochloric acid is applied (effervescence). Often contains visible fossils of marine organisms. Commonly found in former seabed locations.