sedimentary

Limestone

Calcitic limestone (predominantly calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Typically white to buff-gray, fine- to medium-grained, earthy to dull luster, and commonly thin- to medium-bedded; calcite hardness is Mohs 3, with good rhombohedral cleavage. It effervesces vigorously with dilute hydrochloric acid or vinegar, especially on fresh surfaces.

Identified August 14, 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 mainly from accumulated marine shells, carbonate mud, and skeletal debris, later compacted and cemented; the exposed layers are likely Paleozoic or Mesozoic, depending on locality. The outcrop appears naturally bedded and jointed, with weathering producing slab-like blocks.

Uses & applications

Used for crushed aggregate, road base, cement, lime, building stone, landscaping, and architectural masonry; fossiliferous or attractive varieties are collected and sometimes polished.

Geological facts

Limestone is one of Earth’s most widespread sedimentary rocks and can develop caves, sinkholes, and karst landscapes through dissolution by weakly acidic groundwater.

Field identification & locations

Identify it by bedding, relatively soft weathering, pale color, and acid reaction; common deposits occur in former shallow-marine basins worldwide. The photograph shows a limestone quarry or roadcut, not a single distinct hand specimen.