fossil

Brachiopod or Bivalve Fossil in Limestone

Phylum Brachiopoda or Bivalvia (embedded in Calcium Carbonate matrix)

Hardness: 3 (matrix); Color: Tan, grey, off-white; Luster: Dull/Earthy; Crystal Structure: Trigonal (calcite matrix); Specific Gravity: ~2.7; Distinctive radiating ribs on shell surface.

Hardness: 3 (matrix)
Color: Tan, grey, off-white
Luster: Dull/Earthy

Identified July 19, 2026More fossil →

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Physical properties

Hardness: 3 (matrix); Color: Tan, grey, off-white; Luster: Dull/Earthy; Crystal Structure: Trigonal (calcite matrix); Specific Gravity: ~2.7; Distinctive radiating ribs on shell surface.

Formation & geological history

Formed in marine environments as biological remains settled and were buried under sediment, undergoing permineralization over millions of years (typically Paleozoic to Cenozoic eras).

Uses & applications

Scientific study, educational collections, decorative display, and geological field training.

Geological facts

Brachiopods were extremely common during the Paleozoic era and resemble clams, but they have different internal anatomy and symmetry. This specimen shows a partial cast or mold of the shell exterior.

Field identification & locations

Commonly found in sedimentary limestone outcrops or creek beds. Identification is based on the fan-like ribbed pattern and the presence of a calcareous matrix that reacts (fizzes) with weak acid.

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