sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale), Color: light gray to tan, Luster: dull to earthy, Structure: fine-grained, Cleavage: varies by calcite content, Specific Gravity: 2.5-2.7

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale), Color: light gray to tan, Luster: dull to earthy, Structure: fine-grained, Cleavage: varies by calcite content, Specific Gravity: 2.5-2.7

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also be precipitates from calcium-rich water.

Uses & applications

Extensively used in construction as aggregate, in the manufacture of cement, as a soil conditioner in agriculture, and as a flux in steel making.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock found in karst landscapes where caves and sinkholes are common.

Field identification & locations

Identify in the field by checking for an effervescent reaction (fizzing) when exposed to a drop of dilute hydrochloric acid. Commonly found in quarries and road cuts.