sedimentary

Concretionary limestone or calcarenite pebble

Micritic limestone/calcarenite, primarily calcite (CaCO₃)

AI-generated identification · may be incorrect

Light gray-beige, dull to weakly sugary luster, rounded pebble with numerous small rounded grains or shell-like fragments in a finer matrix; calcite hardness ~3, noncleavage in massive form, specific gravity ~2.7. It should effervesce strongly with dilute hydrochloric acid or vinegar, though vinegar may react slowly.

Identified August 13, 2026More sedimentary →

Explore Concretionary limestone or calcarenite pebble 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

Likely formed as carbonate sediment cemented by calcite in a shallow marine or freshwater environment, then rounded by transport. The exact geological age cannot be determined from the photograph; limestone ranges from Precambrian to modern.

Uses & applications

Common limestone is used for aggregate, cement, lime, road base, and building stone; this small specimen has mainly educational or collecting value.

Geological facts

The circular features may be ooids, peloids, or fossil fragments rather than true crystals. Weathering can preferentially expose the carbonate grains, creating the spotted texture.

Field identification & locations

Look for a powdery streak and acid fizz, and distinguish it from concrete by its natural, irregular grain fabric and absence of uniform manufactured aggregate. Common worldwide, especially in former seabeds and carbonate river gravels.