sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: yellowish-tan, beige, buff, to gray with iron oxidation staining; Luster: earthy, dull; Texture: fine-grained, grainy, porous; Reacts vigorously with dilute hydrochloric acid.

Hardness: 3 on Mohs scale
Luster: earthy, dull

Identified July 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily in shallow, warm marine environments through the accumulation and compaction of organic debris such as shells, coral, and algal remains, or chemical precipitation of calcium carbonate over millions of years.

Uses & applications

Widely used in construction, road base, concrete manufacturing, soil conditioning (agricultural lime), dimension stone, and landscaping.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. Acid rain slowly dissolves limestone, leading to karst landscapes featuring caves, sinkholes, and underground rivers.

Field identification & locations

Identified in the field by its light color, soft hardness (scratched easily with a steel nail), dull earthy texture, and effervescence (bubbling) when tested with weak acid. Commonly found in sedimentary basins worldwide.