sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale. Color: White, cream, or light tan. Luster: Dull to earthy. Crystal Structure: Trigonal (as calcite). Cleavage: Perfect rhombohedral (in crystalline forms). Specific Gravity: 2.5-2.7.

Hardness: 3 on Mohs scale
Color: White, cream, or light tan
Luster: Dull to earthy

Identified March 4, 2026More sedimentary →

Explore Limestone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed primarily in shallow 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

Extensively used in construction as an aggregate for concrete and road base, in the manufacture of cement, as a flux in steel making, and as a soil conditioner in agriculture.

Geological facts

Limestone covers about 10% of the Earth's land surface and is the primary rock found in karst landscapes, where it dissolves to create massive cave systems. Most limestone contains significant quantities of fossils.

Field identification & locations

Identify in the field by its light color and its effervescence (fizzing) when a drop of diluted hydrochloric acid is applied. It is commonly found in quarry sites, road cuts, and regions with ancient sea beds.