sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness 3 on the Mohs scale, earthy dull luster, grey to light brown color, reacts with dilute hydrochloric acid, massive to fine-grained sedimentary texture.

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness 3 on the Mohs scale, earthy dull luster, grey to light brown color, reacts with dilute hydrochloric acid, massive to fine-grained sedimentary texture.

Formation & geological history

Forms primarily in shallow, warm marine environments from the accumulation and compaction of organic debris like shells, coral, and algal remains, or by chemical precipitation of calcium carbonate.

Uses & applications

Widely used in construction as building stone, crushed stone for road base, aggregate in concrete, and as a key raw material in cement production.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains abundant fossils of ancient marine organisms.

Field identification & locations

Identify in the field by its soft nature (can be scratched by a steel nail) and characteristic fizzing reaction when exposed to weak acid. Found globally in sedimentary basin formations.