fossil

Seashell Fossil

Invertebrate fossil (phylum Mollusca)

Hardness typically 3 to 4 on Mohs scale (depending on mineralization), color varies from white and tan to grey, vitreous or dull luster, internal crystalline structure often replaced by calcite or aragonite.

Identified July 31, 2026More fossil →

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Physical properties

Formation & geological history

Formed when marine mollusk shells are rapidly buried in sediment such as sand or mud, preventing decay. Over long periods, minerals dissolved in groundwater percolate through the shell, replacing the original organic or carbonate material with stone in a process called permineralization or recrystallization.

Uses & applications

Used in educational exhibits, fossil collecting, decorative items, and scientific research to study paleoenvironments and evolutionary history.

Geological facts

Fossilized shells provide a detailed record of ancient marine environments and climate changes over hundreds of millions of years. They are among the most common and accessible fossils found by amateur collectors.

Field identification & locations

Identified by recognizable ridges, spirals, or symmetrical shapes characteristic of bivalves or gastropods. Commonly found in sedimentary rock formations, especially limestones, shales, and sandstone exposures near ancient coastlines or seabeds.

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Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

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Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

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Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

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Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

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Fossiliferous Limestone

Limestone with embedded fossil cross-section

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Fossiliferous Limestone with Crinoid stems

Limestone (CaCO3) containing Crinoidea fossils

sedimentary