sedimentary

Fossil Shell Fragment (possibly Brachiopod or Bivalve)

Calcium Carbonate (CaCO3) - Phylum Brachiopoda or Mollusca

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: Cream to off-white; Luster: Dull/pearly; Structure: Distinct parallel ribbing/costae; Cleavage: None (concretionary/organic growth); Specific Gravity: ~2.7

Hardness: 3 (Mohs scale)
Color: Cream to off-white
Luster: Dull/pearly

Identified March 7, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: Cream to off-white; Luster: Dull/pearly; Structure: Distinct parallel ribbing/costae; Cleavage: None (concretionary/organic growth); Specific Gravity: ~2.7

Formation & geological history

Formed through the accumulation of organic marine remains in shallow sea environments; typically embedded in limestone or shale during the Paleozoic or Mesozoic eras (approx. 66 to 500 million years ago).

Uses & applications

Primarily used for scientific research, education, and as a low-cost entry point for fossil collecting.

Geological facts

Many of these fossils are 'index fossils,' used by geologists to determine the relative age of the rock layers in which they are found. Brachiopods were far more common than clams before the Permian mass extinction.

Field identification & locations

Identify in the field by looking for symmetrical 'fan-like' shapes with ridges in sedimentary limestone outcrops. Common in the American Midwest and fossiliferous regions of Europe.