sedimentary

Brachiopod Fossil

Phylum Brachiopoda (replaced by Calcite or Silica)

AI-generated identification · may be incorrect

Hardness: 3-4 (if calcite) or 7 (if silica); Color: Gray, tan, or brown; Luster: Dull to earthy; Structure: Bilateral symmetry with fan-shaped ribbing; Cleavage: None (fossilized shell)

Hardness: 3-4 (if calcite) or 7 (if silica)
Color: Gray, tan, or brown
Luster: Dull to earthy

Identified June 15, 2026More sedimentary →

Explore Brachiopod Fossil in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3-4 (if calcite) or 7 (if silica); Color: Gray, tan, or brown; Luster: Dull to earthy; Structure: Bilateral symmetry with fan-shaped ribbing; Cleavage: None (fossilized shell)

Formation & geological history

Formed through the process of permineralization or replacement in marine sedimentary environments. These organisms flourished during the Paleozoic era (541 to 252 million years ago).

Uses & applications

Primarily used for geological dating (index fossils), scientific research, educational purposes, and as collector specimens.

Geological facts

Brachiopods are often called 'lamp shells' because their shape resembles ancient oil lamps. Although they look like clams, they are biologically distinct and have symmetry across the valves rather than between them.

Field identification & locations

Identify by looking for a 'hinge line' where two shells meet and distinct radial ribbing. Commonly found in limestone outcrops, road cuts through sedimentary rock, and dry creek beds.