sedimentary

Rounded limestone pebble

Micritic limestone, primarily calcite (CaCO₃)

AI-generated identification · may be incorrect

Cream to light gray, dull-to-waxy luster, fine-grained and weakly porous, with small pits or fossil-like cavities. Mohs hardness 3; calcite shows strong effervescence with dilute hydrochloric acid and commonly has indistinct cleavage in massive limestone.

Identified September 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted carbonate mud and/or microscopic marine shells, later lithified into limestone; its smooth shape indicates erosion and transport by water or waves. The geological age cannot be determined from the photograph.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and soil conditioner; this small weathered pebble has little commercial or jewelry value.

Geological facts

Limestone is chemically soluble in weak acids, producing caves, sinkholes, and karst landscapes. Surface pits may represent dissolved shell fragments, pores, or weathering cavities rather than visible fossils.

Field identification & locations

Common in riverbeds, beaches, glacial deposits, and areas underlain by carbonate bedrock worldwide. Confirm with a vinegar or dilute-acid fizz test on a fresh scratch; a steel nail should not easily scratch it, while a knife may.