Rock Identifier
Fossilized shell fragment (Likely calcitic or aragonitic bivalve/gastropod shell; exact taxon indeterminate) — fossil
fossil

Fossilized shell fragment

Likely calcitic or aragonitic bivalve/gastropod shell; exact taxon indeterminate

AI-generated identification · may be incorrect

Cream to tan, strongly ribbed and layered, with dull to pearly luster; shell material is typically Mohs 3–4, has curved growth lines and may fizz weakly in dilute acid. It appears paired with a polished yellow chalcedony or calcite-like stone, which is also geological material.

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Physical properties

Cream to tan, strongly ribbed and layered, with dull to pearly luster; shell material is typically Mohs 3–4, has curved growth lines and may fizz weakly in dilute acid. It appears paired with a polished yellow chalcedony or calcite-like stone, which is also geological material.

Formation & geological history

A marine mollusk shell formed from calcium carbonate and was later buried, mineralized, and weathered from sedimentary rock; age cannot be determined from the image. Such fossils commonly originate in Paleozoic–Cenozoic marine limestones.

Uses & applications

Collected as a fossil specimen and used in educational displays, jewelry, and decorative cabochons; the accompanying polished stone may be used in jewelry.

Geological facts

The ribbing and growth increments reflect shell growth and species adaptation, not mineral crystal banding.

Field identification & locations

Look for bilateral or spiral shell geometry, growth lines, ribs, and carbonate composition; common sources include marine limestone deposits worldwide. Typical value is about $5–$30 for a small common fragment, or $30–$100+ if unusually complete or well-prepared.

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Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

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Bioclastic limestone, composed chiefly of calcite (CaCO₃)

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Weathered fossil bone fragment (identification uncertain)

Fossilized bone; exact taxon and mineral composition cannot be determined from the image

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