fossil

Fossiliferous limestone pebble

Bioclastic limestone, likely coral-rich (calcium carbonate, CaCO₃; commonly calcite)

AI-generated identification · may be incorrect

Gray-brown, rounded and weathered, with pale polygonal fossil structures resembling colonial coral or bryozoan. Calcite has Mohs hardness 3, vitreous-to-dull luster, rhombohedral cleavage, and reacts vigorously with dilute hydrochloric acid.

Identified August 29, 2026More fossil →

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Physical properties

Formation & geological history

Formed when marine skeletal debris accumulated, lithified, and later eroded into a pebble; the fossils likely date from the Paleozoic or Mesozoic, depending on locality. The exact age cannot be determined from the photograph alone.

Uses & applications

Used mainly for education, collecting, and decorative display; limestone is also important in cement, lime, aggregate, and building stone.

Geological facts

The pale reticulated pattern may represent fossilized colonial coral, but weathered calcite veins or other bioclasts are possible. A vinegar test may produce weak fizz; hydrochloric acid is more diagnostic.

Field identification & locations

Identify by its low hardness, abundant fossil pattern, and acid reaction; avoid confusing it with chert, which is harder and does not fizz. Fossiliferous limestones occur widely in former shallow-marine regions worldwide.