Rock Identifier
Fossilized bivalve shell fragment (Pectinid or related scallop bivalve; shell originally composed mainly of calcite (CaCO₃)) — fossil
fossil

Fossilized bivalve shell fragment

Pectinid or related scallop bivalve; shell originally composed mainly of calcite (CaCO₃)

AI-generated identification · may be incorrect

A ribbed, fan-shaped shell fragment with dark gray-brown mineralization and a dull to slightly waxy luster. Calcite shell material is Mohs hardness 3, with excellent cleavage; specific gravity is about 2.7, though fossilization can alter these properties.

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Physical properties

A ribbed, fan-shaped shell fragment with dark gray-brown mineralization and a dull to slightly waxy luster. Calcite shell material is Mohs hardness 3, with excellent cleavage; specific gravity is about 2.7, though fossilization can alter these properties.

Formation & geological history

This is likely a marine bivalve fossil preserved by burial, compaction, and mineral replacement or staining in sedimentary rock. Its exact geological age cannot be determined from the photograph; scallop-like fossils range from the Paleozoic to the Recent.

Uses & applications

Primarily a collectible, teaching specimen, or decorative fossil; it has little industrial value compared with limestone or shell aggregate.

Geological facts

The regularly spaced radial ribs are characteristic of scallop- and fan-shell relatives and helped strengthen the shell against wave and predation forces.

Field identification & locations

Identify it by its fan shape, repeated ribs, bilateral shell symmetry, and curved growth lines; common fossil-bearing marine limestones and sandstones worldwide contain similar specimens. A microscope or locality information is needed for precise identification.

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