fossil

Fossilized Gastropod Steinkern

Class Gastropoda internal mold

Hardness: 3-4 (calcite matrix), Color: Off-white to pale tan with orange-brown weathering spots, Luster: Earthy to dull, Structure: Amorphous internal cast of a spiral shell

Identified August 2, 2026More fossil →

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Physical properties

Hardness: 3-4 (calcite matrix), Color: Off-white to pale tan with orange-brown weathering spots, Luster: Earthy to dull, Structure: Amorphous internal cast of a spiral shell

Formation & geological history

Formed in marine or freshwater sedimentary environments during the Paleozoic, Mesozoic, or Cenozoic eras when sediment filled the empty shell of a dead gastropod and hardened into rock while the original shell dissolved away.

Uses & applications

Used in educational displays, fossil collecting, and studying ancient paleoenvironments.

Geological facts

A steinkern is formed when the inside of a fossil shell becomes filled with mud or sediment, which hardens into rock. Later, the original shell material dissolves away, leaving just the internal rocky cast behind.

Field identification & locations

Found commonly in limestone and shale deposits worldwide; identifiable by the distinct whorl impression or hollowed-out concave areas left behind by the internal structure of the original mollusk.

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