fossil

Bivalve Internal Mold Fossil

Steinkern (Bivalvia mold)

AI-generated identification · may be incorrect

Hardness: variable (3-4 if limestone/calcite, 6-7 if silicified); Color: grey to tan with earthy texture; Luster: dull/non-reflective; Shape: asymmetrical oval resembling a heart or shell; No visible external shell material.

Hardness: variable (3-4 if limestone/calcite, 6-7 if silicified)
Color: grey to tan with earthy texture
Luster: dull/non-reflective

Identified July 18, 2026More fossil →

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Physical properties

Formation & geological history

Formed during the Mesozoic or Cenozoic eras when sediment filled a clam or mussel shell after the animal died. The shell eventually dissolved, leaving a hardened sediment 'cast' of the interior cavity.

Uses & applications

Primarily for educational purposes, paleontological study, and amateur fossil collecting.

Geological facts

These fossils are often called 'heart stones' or 'deer hearts' because their shape can mimic a mammalian heart. In some cultures, they were considered luck charms.

Field identification & locations

Check for concentric growth lines or a symmetrical 'beak' at the hinge point. Frequently found in limestone quarries, coastal cliffs, and riverbeds where sedimentary layers are exposed.