sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Grey, tan, or buff; Luster: Dull to earthy; Structure: Massive or fine-grained; Cleavage: None (conchoidal fracture); Specific Gravity: 2.3 to 2.7

Hardness: 3 on Mohs scale
Color: Grey, tan, or buff
Luster: Dull to earthy

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Grey, tan, or buff; Luster: Dull to earthy; Structure: Massive or fine-grained; Cleavage: None (conchoidal fracture); Specific Gravity: 2.3 to 2.7

Formation & geological history

Formed in marine environments from 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

Used primarily in construction for road base, concrete aggregate, and building stone. It is also used as a soil conditioner and in the production of cement and lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains fossils of prehistoric marine life, which help geologists date the rock layer.

Field identification & locations

Identify in the field by applying a small amount of household vinegar (cold dilute hydrochloric acid); it will effervesce (fizz) due to its carbonate content. Commonly found in areas that were once prehistoric seafloads.