fossil

Bivalve Fossil (Mussel or Clam Shell)

Bivalvia

Hardness: 3-4 (calcite/aragonite); Color: Bluish-grey to dark brown with concentric growth lines; Luster: Pearly to dull; Crystal Structure: Orthorhombic or trigonal (calcium carbonate); Specific Gravity: 2.5-2.8

Hardness: 3-4 (calcite/aragonite)
Color: Bluish-grey to dark brown with concentric growth lines
Luster: Pearly to dull

Identified August 3, 2026More fossil →

Explore Bivalve Fossil (Mussel or Clam Shell) in the encyclopedia →

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Physical properties

Formation & geological history

Formed through the fossilization or preservation of marine or freshwater mollusk shells in sedimentary environments, often ranging from the Paleozoic era to recent geological epochs.

Uses & applications

Used in paleontological studies, educational displays, decorative items, and fossil collecting.

Geological facts

Bivalves first appeared during the Cambrian period over 500 million years ago and are excellent index fossils for dating sedimentary rock layers.

Field identification & locations

Found worldwide in sedimentary rock formations, particularly in ancient marine, estuarine, and lake deposits. Look for asymmetrical, two-part hinged shells embedded in limestone, shale, or sandstone.