sedimentary

Fossiliferous Limestone Pebble

Calcium Carbonate (CaCO3) with Biogenic Inclusions

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs), Color: Light gray matrix with dark gray fossil inclusions, Luster: Dull/Earthy, Crystal Structure: Microcrystalline (micrite), Cleavage: None (conchoidal to irregular fracture)

Identified June 25, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs), Color: Light gray matrix with dark gray fossil inclusions, Luster: Dull/Earthy, Crystal Structure: Microcrystalline (micrite), Cleavage: None (conchoidal to irregular fracture)

Formation & geological history

Formed in a shallow marine environment where carbonate mud (calcareous ooze) accumulated over fossil remains, followed by lithification over millions of years. This specimen has been rounded by wave or river action.

Uses & applications

Limestone is used extensively in construction, cement production, and as an industrial flux; fossiliferous specimens are popular for education and hobbyist collecting.

Geological facts

The dark shapes in the stone represent cross-sections of ancient marine organisms, likely fragments of bivalve shells or gastropods that lived millions of years ago.

Field identification & locations

Check for a positive reaction (fizzing) when a drop of weak acid like vinegar is applied. Found commonly on beaches, stream beds, and in sedimentary basins globally.