sedimentary

Limestone

Sedimentary rock composed of Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: Gray to light tan with orange weathering crust; Luster: Dull/Earthy; Structure: Fine-grained, microcrystalline; Cleavage: None (conchoidal to irregular fracture).

Hardness: 3 (Mohs scale)
Color: Gray to light tan with orange weathering crust
Luster: Dull/Earthy

Identified April 6, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: Gray to light tan with orange weathering crust; Luster: Dull/Earthy; Structure: Fine-grained, microcrystalline; Cleavage: None (conchoidal to irregular fracture).

Formation & geological history

Formed by the accumulation of shell, coral, algal, and fecal debris in marine environments, or via chemical precipitation. This specific specimen shows weathering of iron minerals, creating the orange exterior.

Uses & applications

Primary source of lime for cement, used as a building stone, road base, and in agricultural soil treatment to neutralize acidity.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is essential for the formation of caves and karst landscapes due to its solubility in slightly acidic water.

Field identification & locations

Identified in the field by its gray color and strong bubbling reaction when exposed to dilute hydrochloric acid. It often contains visible fossils. Common in historically submerged oceanic plates.