sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3-4 (Mohs scale); Color: Gray, tan, or buff; Luster: Dull to earthy; Structure: Microcrystalline or clastic; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.5-2.7

Hardness: 3-4 (Mohs scale)
Color: Gray, tan, or buff
Luster: Dull to earthy

Identified July 7, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: Gray, tan, or buff; Luster: Dull to earthy; Structure: Microcrystalline or clastic; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.5-2.7

Formation & geological history

Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also form chemically through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used in construction as an aggregate for road bases, in the manufacture of cement, as a decorative building stone, and in agricultural soil conditioning.

Geological facts

Limestone is the source of approximately 10% of the total volume of all sedimentary rocks. Many world-famous caves and karst landscapes are carved into thick limestone deposits.

Field identification & locations

Identification: Reacts strongly (fizzes) with cold diluted hydrochloric acid. Look for a fine-grained, gray surface often showing faint layers or fossils in outcrops.