fossil

Fossil Shell (Brachiopod or Mollusk)

Phylum Brachiopoda or Class Bivalvia (e.g., Mucrospirifer or similar genus)

AI-generated identification · may be incorrect

Hardness: 3-4 (if calcified/silicified), Color: Dark gray to black (carbonized), Luster: Dull to earthy, Structure: Ribbed or costate radial patterns, specific gravity: ~2.7

Identified July 1, 2026More fossil →

Explore Fossil Shell (Brachiopod or Mollusk) 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 calcified/silicified), Color: Dark gray to black (carbonized), Luster: Dull to earthy, Structure: Ribbed or costate radial patterns, specific gravity: ~2.7

Formation & geological history

Formed in marine sedimentary environments where the organism was buried by silt or mud. Through permineralization or carbonization, the organic shell was replaced or preserved. Often dates to the Paleozoic or Mesozoic eras.

Uses & applications

Primarily used for educational purposes, scientific research (stratigraphy), and amateur fossil collecting.

Geological facts

Fossils like these are 'index fossils,' helping geologists date the rock layer they are found in. This dark coloration suggests a carbon-rich environment or anaerobic preservation conditions.

Field identification & locations

Identify by looking for symmetrical radial ridges and a shell-like shape within sedimentary rocks like shale or limestone. Found globally in ancient seabed deposits.