fossil

Fossil shell fragment, likely brachiopod or bivalve

Indeterminate fossilized marine mollusk or brachiopod; mineralized calcite shell in a carbonate matrix

AI-generated identification · may be incorrect

Dark gray-brown, irregularly layered specimen with cream-colored mineralized bands and apparent shell growth/lamination. Likely Mohs 3–4 if calcitic, with dull to slightly earthy luster; exact crystal structure and specific gravity cannot be confirmed from the image.

Identified August 17, 2026More fossil →

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At a glance

Common name: Fossil shell fragment, likely brachiopod or bivalve
Scientific name: Indeterminate fossilized marine mollusk or brachiopod; mineralized calcite shell in a carbonate matrix
Category: fossil
Identified: August 17, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a small common fragment; $50–$150 or more if species identification, preservation, locality, or preparation is exceptional.

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

Probably formed when a marine shell was buried in carbonate sediment and gradually replaced or infilled by calcite during lithification, commonly in Paleozoic–Mesozoic sedimentary rocks. The visible dark material may be limestone, shale, or iron/manganese-stained matrix.

Uses & applications

Primarily a teaching, collecting, and display specimen; not generally used in construction or jewelry, though polished fossil material can be decorative.

Geological facts

The repeated curved bands resemble shell growth layers rather than igneous crystals. Distinguishing a brachiopod from a bivalve requires viewing the hinge, symmetry, and complete shell profile.

Field identification & locations

Look for bilateral shell symmetry, radiating ribs, hinge structures, and a carbonate reaction to dilute hydrochloric acid; avoid acid testing if preservation matters. Common sources include marine Paleozoic limestone beds worldwide.