sedimentary

Rounded limestone pebble

Micritic or bioclastic limestone, primarily calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Typically Mohs hardness 3, cream to tan, dull to subtly waxy luster, very fine-grained and massive; may contain faint fossil or shell fragments. It should effervesce with dilute hydrochloric acid, distinguishing it from quartz-rich rocks.

Identified September 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted carbonate mud, skeletal debris, or precipitated calcite in a marine or freshwater basin, then rounded by stream or coastal abrasion. Its exact geological age cannot be determined visually and may range from Paleozoic to modern sedimentary deposits.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and landscaping material; attractive polished pieces are inexpensive decorative specimens.

Geological facts

The smooth shape indicates prolonged transport or wave action rather than its original depositional form. Weathering can produce the cream, tan, and rusty surface tones visible here.

Field identification & locations

Common in limestone regions, river gravels, beaches, and quarries worldwide; confirm with acid fizz and a steel-knife scratch. Avoid acid testing if the specimen is valuable or polished.