sedimentary

Fossiliferous Limestone with Brachiopods

Calcium Carbonate (CaCO3) with fossilized Brachiopoda sp. (likely Order Spiriferida or Rhynchonellida)

AI-generated identification · may be incorrect

Hardness: 3-4 (matrix); Color: Tan, beige, or light brown with darker grey fossil imprints; Luster: Dull/Earthy; Structure: Clastic or biometric sedimentary layer; Specific Gravity: 2.3-2.7

Hardness: 3-4 (matrix)
Color: Tan, beige, or light brown with darker grey fossil imprints
Luster: Dull/Earthy

Identified March 30, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (matrix); Color: Tan, beige, or light brown with darker grey fossil imprints; Luster: Dull/Earthy; Structure: Clastic or biometric sedimentary layer; Specific Gravity: 2.3-2.7

Formation & geological history

Formed in shallow marine environments where skeletal debris (shells) accumulated on the sea floor and were compressed over millions of years. Most common in Paleozoic era rock formations (approx. 250-500 million years old).

Uses & applications

Primarily used for geological education, fossil collecting, and occasionally as structural stone or crushed aggregate if found in massive quantities. High-quality specimens are used for teaching paleontological index fossils.

Geological facts

Brachiopods are not mollusks, despite their shell appearance; they belong to a distinct phylum. They are excellent 'index fossils,' helping geologists date the rock layer in which they are found due to their wide distribution and specific time ranges.

Field identification & locations

Identify by looking for symmetrical 'lamp-shell' shapes with distinct ribbing patterns (costae) embedded in a fine-grained matrix. Common in limestone outcrops or riverbeds in the American Midwest (Cincinnatian) and parts of Europe.