sedimentary

Rounded limestone pebble

Calcite-rich micritic limestone (CaCO₃), possibly a fossiliferous limestone

AI-generated identification · may be incorrect

Gray-brown, fine-grained, dull to slightly earthy luster, rounded by abrasion; calcite has Mohs hardness 3 and strong effervescence in dilute hydrochloric acid. Crystal structure is trigonal, though microscopic grains are not visibly crystalline; cleavage is indistinct in the compact rock.

Identified August 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from lithified carbonate mud and/or shell debris in a marine environment, then rounded by stream, beach, or glacial transport. Its exact geological age cannot be determined from the photograph; limestones range from recent to Precambrian.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and soil conditioner; this small specimen has mainly educational or collecting value.

Geological facts

The pale irregular patches may be calcite veins, weathered shell fragments, or minor cavities rather than distinct fossils.

Field identification & locations

Look for a relatively soft, opaque gray stone and test a fresh surface with vinegar or dilute acid for bubbling; avoid confusing it with dolostone, which reacts weakly. Common in limestone regions, riverbeds, beaches, and glacial deposits.