fossil

Fossilized bivalve shell in limestone

Calcitic fossil shell; likely an oyster or other rudist/bivalve (Bivalvia), preserved in carbonate rock

AI-generated identification · may be incorrect

The specimen shows strong radial ribs and a thick, irregular shell form, with cream, gray, and tan coloration and a dull to slightly waxy luster. Shell material is mainly calcite (Mohs 3), commonly effervescing with dilute hydrochloric acid; the surrounding matrix is limestone.

Identified August 8, 2026More fossil →

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At a glance

Common name: Fossilized bivalve shell in limestone
Scientific name: Calcitic fossil shell; likely an oyster or other rudist/bivalve (Bivalvia), preserved in carbonate rock
Category: fossil
Identified: August 8, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $50–$150 or more if the species, locality, preservation, or provenance 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

A marine bivalve was buried in carbonate sediment that lithified into limestone, with later mineral replacement and weathering producing the mottled surface. Exact geological age and species require locality and detailed examination; similar fossils range from Paleozoic to Cenozoic strata.

Uses & applications

Primarily a collectible and educational fossil; carbonate matrix may be used decoratively, but this small specimen has no significant industrial value.

Geological facts

The ribbed surface represents original shell ornamentation, while tan areas may be iron-oxide staining or matrix. Fossil shells are often preserved as molds, casts, recrystallized calcite, or partially replaced shell.

Field identification & locations

Look for bilateral shell symmetry, repeated radial ribs, and acid-reactive carbonate material; distinguish it from modern shell by mineralized texture and rock matrix. Common in marine limestone deposits worldwide.