fossil

Fossiliferous shale or mudstone with a brachiopod fossil

Likely a spiriferid brachiopod fossil in dark shale/mudstone; exact species and age require locality and examination

AI-generated identification · may be incorrect

Dark gray to brown, fine-grained matrix with layered bedding and a prominent ribbed, fan-shaped fossil impression or shell. Matrix hardness is roughly Mohs 2–4; fossil shell may be calcite (Mohs 3), with dull to subvitreous luster and sedimentary lamination.

Identified August 16, 2026More fossil →

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At a glance

Common name: Fossiliferous shale or mudstone with a brachiopod fossil
Scientific name: Likely a spiriferid brachiopod fossil in dark shale/mudstone; exact species and age require locality and examination
Category: fossil
Identified: August 16, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $50–$200+ if the fossil is exceptionally complete, attractive, or from a documented locality.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed when marine mud buried and preserved a brachiopod shell, commonly during the Paleozoic Era (about 541–252 million years ago), then lithified into shale or mudstone.

Uses & applications

Primarily a teaching, collecting, and decorative specimen; scientifically valuable for biostratigraphy and reconstructing ancient marine environments, but generally not used commercially.

Geological facts

The radial ribs and bilateral symmetry are characteristic of brachiopods, which are distinct from bivalve mollusks because their two valves are unequal and arranged dorsoventrally.

Field identification & locations

Look for repeated radial ribs, a central fold or sulcus, and alignment with sedimentary bedding; common in Paleozoic marine sedimentary rocks worldwide, especially North America and Europe. Avoid acid testing the fossil unless prepared for possible calcite reaction.