sedimentary

Fossiliferous limestone pebble

Bioclastic limestone, chiefly calcite (CaCO₃)

AI-generated identification · may be incorrect

Light brown-gray, fine-grained and dull to subtly waxy, with abundant pale fossil fragments or shell cross-sections. Calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.7; it should fizz with dilute hydrochloric acid or vinegar if freshly exposed.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented marine skeletal debris in shallow seas, commonly during the Paleozoic–Cenozoic; the exact age cannot be determined from the photograph. Weathering and transport rounded it into the displayed pebble.

Uses & applications

Used as crushed stone, aggregate, cement and lime feedstock, and decorative facing stone; attractive polished pieces are collected or used as ornaments. This small specimen generally has modest commercial value.

Geological facts

The pale patterns likely represent fossil shells, bryozoans, crinoid fragments, or dissolution-filled cavities rather than mineral crystals. Limestone can preserve detailed evidence of ancient marine ecosystems.

Field identification & locations

Look for acid effervescence, a relatively soft surface that scratches with steel, and visible fossil textures; avoid confusing it with marble, which has recrystallized grains and usually lacks distinct fossils. Common worldwide in former shallow-marine sedimentary basins.