sedimentary
Fossilized Brachiopod Shell
Phylum Brachiopoda (likely Order Spiriferida or Strophomenida)
Hardness: 3-4 (calcite); Color: Off-white to tan/cream; Luster: Dull to pearly/waxy; Structure: Symmetrical bivalved shell appearance but with internal folding; Specific Gravity: ~2.7
- Hardness
- 3-4 (calcite)
- Color
- Off-white to tan/cream
- Luster
- Dull to pearly/waxy
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Physical properties
Hardness: 3-4 (calcite); Color: Off-white to tan/cream; Luster: Dull to pearly/waxy; Structure: Symmetrical bivalved shell appearance but with internal folding; Specific Gravity: ~2.7
Formation & geological history
Formed through permineralization of marine organisms in shallow sea environments. Given the coordinates (Louisville, KY area), this likely dates to the Devonian or Ordovician periods (approx. 360-450 million years ago).
Uses & applications
Used primarily for educational purposes, scientific research, and as collector specimens. Occasionally used in jewelry if polished.
Geological facts
Brachiopods are not mollusks, though they look like clams. They are one of the most common fossils found in the Ohio River Valley region due to the presence of the Falls of the Ohio archaeological and geological beds.
Field identification & locations
Identify by looking for bilateral symmetry across the valves and distinct growth lines or ribbing. Very common in the limestone beds of Kentucky and Indiana. Check for a hole (foramen) where the stalk (pedicle) once emerged.
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