fossil

Polished fossil shell fragment (likely ammonite or bivalve)

Fossilized mollusk shell; likely aragonite/calcite replaced by silica or iron-rich minerals

AI-generated identification · may be incorrect

Dark brown-black, glossy, smoothly polished, with curved shell-like banding and possible rib or growth structures. Original shell mineral was commonly aragonite or calcite; hardness is approximately 3–7 depending on replacement, with no clearly visible crystal structure.

Identified September 3, 2026More fossil →

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At a glance

Common name: Polished fossil shell fragment (likely ammonite or bivalve)
Scientific name: Fossilized mollusk shell; likely aragonite/calcite replaced by silica or iron-rich minerals
Category: fossil
Identified: September 3, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a small common polished fragment; $50–$150+ if identified, attractive, and 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 a marine mollusk shell was buried in sediment and mineralized during diagenesis, typically over millions of years; exact age and identity cannot be confirmed from the image alone.

Uses & applications

Primarily a collectible, jewelry, or ornamental specimen; polished fossil fragments are sometimes mounted as pendants or used in cabochons.

Geological facts

The visible curved layering resembles fossil shell growth lines, though a polished dark agate or mineralized wood fragment is also possible.

Field identification & locations

Look for consistent biological symmetry, growth lines, ribs, chambers, or shell curvature; acid testing is risky and inconclusive on polished material. Comparable fossils occur in marine limestone and shale worldwide.