fossil

Bivalve Fossil (Clam Stone)

Phylum Mollusca, Class Bivalvia

AI-generated identification · may be incorrect

Hardness: 3-4 (if limestone) to 7 (if silicified); Color: Grey, tan, or brown; Luster: Dull/earthy; Internal mold showing symmetrical valves; Specific gravity: 2.6-2.8

Hardness: 3-4 (if limestone) to 7 (if silicified)
Color: Grey, tan, or brown
Luster: Dull/earthy

Identified July 10, 2026More fossil →

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Physical properties

Hardness: 3-4 (if limestone) to 7 (if silicified); Color: Grey, tan, or brown; Luster: Dull/earthy; Internal mold showing symmetrical valves; Specific gravity: 2.6-2.8

Formation & geological history

Formed through the lithification of marine sediments. The organic shell dissolves over time, leaving a sediment-filled mold or a mineral-replaced cast. Most common in Paleozoic to Cenozoic marine strata.

Uses & applications

Scientific study, educational collections, and decorative garden/landscape stones.

Geological facts

Bivalves have existed for over 500 million years. This specific shape is an 'internal mold' or 'steinkern,' which is the rock that hardened inside the shell before the shell itself dissolved.

Field identification & locations

Found in sedimentary outcrops, riverbeds, and coastal regions globally. Identification is based on the heart or nut-like shape with a visible hinge line (commissure) where the two valves met.