sedimentary

Fossiliferous limestone pebble

Micritic to bioclastic limestone, composed mainly of calcite (CaCO₃)

AI-generated identification · may be incorrect

Gray-brown, rounded and water-worn, with granular texture and apparent fossil or shell fragments/voids; calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and specific gravity about 2.7. It should fizz briskly with dilute hydrochloric acid or vinegar if sufficiently fresh and exposed.

Identified September 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented carbonate mud and marine skeletal debris, likely deposited in a shallow-marine environment; the exact geological age cannot be determined from the image and may range from Paleozoic to Cenozoic. Later erosion shaped it into a smooth pebble.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and occasionally as a fossil-bearing decorative or educational specimen; this piece is primarily a collectible.

Geological facts

The cavities likely represent dissolved shells or other bioclasts, while the dark coloration may reflect organic matter or weathering. Surface patina and rounding indicate prolonged exposure to running water or surf.

Field identification & locations

Common in limestone-bearing river gravels, beaches, and quarry debris; inspect cavities for recognizable shell forms and perform an acid test on an inconspicuous spot. Estimated value: $2–$15 as a common pebble, or roughly $15–$50 if fossils are clearly identifiable.