sedimentary

Limestone

Calcium Carbonate (CaCO3)

Mohs hardness of 3; color varies from white, gray, yellow to tan; dull to earthy luster; crystal structure is hexagonal (calcite); cleavage is rhombohedral; specific gravity is 2.71.

Identified July 31, 2026More sedimentary →

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Physical properties

Mohs hardness of 3; color varies from white, gray, yellow to tan; dull to earthy luster; crystal structure is hexagonal (calcite); cleavage is rhombohedral; specific gravity is 2.71.

Formation & geological history

Formed by the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, or through the chemical precipitation of calcium carbonate from water in marine or freshwater environments.

Uses & applications

Widely used in the construction industry for crushed stone in road base, as an aggregate for concrete, as a primary component in manufacturing Portland cement, and in agriculture for neutralizing acidic soils.

Geological facts

Limestone formations often contain well-preserved fossils and can form spectacular karst topography features like caves, sinkholes, and underground rivers due to its solubility in slightly acidic water.

Field identification & locations

Can be easily identified in the field by its light color range and a characteristic fizz or effervescence when a drop of dilute hydrochloric acid (or vinegar) is applied.