fossil

Fossil Bivalve / Ostreid Shell (Hag Stone / Perforated Pebble)

Phylum Mollusca, Class Bivalvia

Hardness: 3-4 (Calcite/Aragonite); Color: Light grey to white; Luster: Dull to vitreous; Structure: Crystalline calcium carbonate with preserved organic shell matrix.

Hardness: 3-4 (Calcite/Aragonite)
Color: Light grey to white
Luster: Dull to vitreous

Identified August 3, 2026More fossil →

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Physical properties

Hardness: 3-4 (Calcite/Aragonite); Color: Light grey to white; Luster: Dull to vitreous; Structure: Crystalline calcium carbonate with preserved organic shell matrix.

Formation & geological history

Formed in ancient marine environments (shallow seas or coastal areas), where carbonate shells accumulated in sediment and underwent lithification and fossilization over millions of years.

Uses & applications

Used for geological education, fossil collecting, and historically regarded as folk talismans or 'hag stones' for protection.

Geological facts

Many naturally tumbled beach pebbles that feature distinct shapes or inclusions are preserved shells or fossil fragments that have been smoothed by wave action.

Field identification & locations

Found along beaches, riverbeds, and limestone-rich sedimentary formations. Identified by characteristic shell morphology and reaction to dilute hydrochloric acid (effervescence).

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