sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Mohs hardness of 3, light gray to beige color, earthy to dull luster, effervesces vigorously with dilute hydrochloric acid, specific gravity approximately 2.5 to 2.7.

Identified July 23, 2026More sedimentary →

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Physical properties

Mohs hardness of 3, light gray to beige color, earthy to dull luster, effervesces vigorously with dilute hydrochloric acid, specific gravity approximately 2.5 to 2.7.

Formation & geological history

Formed primarily in shallow, warm marine environments from the accumulation and compaction of organic debris such as coral, shell fragments, and fecal matter, as well as chemical precipitation of calcium carbonate.

Uses & applications

Widely used in construction as crushed stone, aggregate, and building stone, in the production of cement and lime, as a soil conditioner in agriculture, and as a fluxing agent in steel manufacturing.

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks. Famous geological features like the White Cliffs of Dover and the landscape of Guilin, China, are made predominantly of limestone.

Field identification & locations

Identified easily in the field using an acid test (fizzes with dilute HCl) and its relative softness (scratched by a copper penny or steel blade). Commonly found worldwide in ancient marine basins and karst topographies.