sedimentary

Weathered limestone pebble

Micritic limestone, primarily calcite (CaCO₃)

AI-generated identification · may be incorrect

Pale cream-gray, fine-grained, dull to slightly earthy luster, rounded by abrasion, with rusty iron-oxide staining and possible tiny fossil or pore marks. Calcite has Mohs hardness 3, rhombohedral cleavage, and reacts vigorously with dilute hydrochloric acid; specific gravity about 2.7.

Identified August 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented carbonate mud or microscopic marine remains, commonly during shallow-marine deposition; its exact geological age cannot be determined from the photograph. Later erosion produced the smooth pebble shape.

Uses & applications

Used for aggregate, cement and lime production, building stone, and landscaping; attractive polished pieces may be sold as inexpensive specimens.

Geological facts

The powder or a fresh scratched surface should fizz with dilute acid, distinguishing limestone from similarly colored quartz-rich rocks. Iron staining developed when groundwater oxidized small amounts of iron-bearing material.

Field identification & locations

Common in sedimentary basins, limestone coasts, river gravels, and glacial deposits worldwide. Look for very fine texture, softness, and acid reaction; avoid relying solely on color because weathering can obscure fossils and grains.