fossil

Fossil shell fragment, likely bivalve or gastropod

Indeterminate molluscan fossil; original shell likely aragonite or calcite (CaCO₃)

AI-generated identification · may be incorrect

Dark gray, smooth to weathered surface with a pronounced cavity and possible shell growth ridges; hardness approximately 3–4 if calcitic, with moderate density and dull to slightly waxy luster. The apparent form is consistent with a worn fossil shell or internal mold, though the image is insufficient for species-level…

Identified August 21, 2026More fossil →

Explore Fossil shell fragment, likely bivalve or gastropod in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Fossil shell fragment, likely bivalve or gastropod
Scientific name: Indeterminate molluscan fossil; original shell likely aragonite or calcite (CaCO₃)
Category: fossil
Identified: August 21, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common unidentified fragment; $30–$150+ if complete, clearly identified, 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 a marine mollusk shell was buried in sediment and mineralized or left as a natural mold; age could range from Paleozoic to Cenozoic and cannot be determined visually. Commonly preserved in limestone, shale, or sandstone.

Uses & applications

Primarily a collector, educational, or decorative specimen; not generally used industrially or in jewelry unless exceptionally preserved or polished.

Geological facts

Shell cavities and curved ridges can survive even after the original carbonate dissolves and is replaced by sediment or minerals. A vinegar test may fizz on exposed calcite, but it can damage the specimen.

Field identification & locations

Look for bilateral shell symmetry, hinge structures, spiral whorls, or regular growth lines; identify the surrounding matrix and scale for a better determination. Common in marine sedimentary rocks worldwide.