fossil

Fossilized bivalve or brachiopod shell

Mineralized carbonate shell, commonly calcite (CaCO₃); exact taxon indeterminate from image

AI-generated identification · may be incorrect

Small brown-gray, irregularly ribbed specimen with visible shell curvature and mineral-filled surface; calcite has Mohs hardness 3, vitreous to dull luster, and perfect rhombohedral cleavage. The texture appears fossilized rather than a crystalline rock.

Identified August 18, 2026More fossil →

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At a glance

Common name: Fossilized bivalve or brachiopod shell
Scientific name: Mineralized carbonate shell, commonly calcite (CaCO₃); exact taxon indeterminate from image
Category: fossil
Identified: August 18, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a small common specimen; $30–$100 or more if the species, locality, preservation, or preparation is documented.

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

Likely a marine shell preserved by burial and replacement or infilling with calcite during diagenesis; age cannot be determined visually, but such fossils commonly range from Paleozoic to Cenozoic strata.

Uses & applications

Primarily a collectible, educational specimen, or display piece; carbonate fossils may also be used in teaching paleontology and stratigraphy, but have negligible industrial value.

Geological facts

Ribbing and bilateral shell symmetry can distinguish brachiopods from bivalves, though the photographed surface is insufficient for confident identification. Brown coloration commonly comes from iron-oxide staining or sediment impregnation.

Field identification & locations

Look for organized ribs, a natural hinge or commissure, shell symmetry, and mineralized internal cavities; genuine fossils usually show sediment matrix and uneven replacement rather than uniform manufactured texture. Common in marine limestone and shale deposits worldwide.