Rock Identifier
Fossil bivalve shell (Fossilized or partially mineralized bivalve; exact genus cannot be determined from the image) — fossil
fossil

Fossil bivalve shell

Fossilized or partially mineralized bivalve; exact genus cannot be determined from the image

AI-generated identification · may be incorrect

A ribbed, coiled-looking shell fragment with brown-orange coloration and pearly luster. Original shell is calcium carbonate (aragonite/calcite); hardness about 3–4 Mohs, with layered growth lines and probable partial mineral replacement.

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Physical properties

A ribbed, coiled-looking shell fragment with brown-orange coloration and pearly luster. Original shell is calcium carbonate (aragonite/calcite); hardness about 3–4 Mohs, with layered growth lines and probable partial mineral replacement.

Formation & geological history

A marine bivalve shell preserved in sediment, later buried and mineralized during diagenesis; its geological age and formation locality require context or matrix examination.

Uses & applications

Primarily valued for education, paleontology, decoration, and collecting; not normally used in construction or jewelry unless cut or polished.

Geological facts

The apparent concentric ridges are growth increments, not crystal faces. Fossil shells may retain original nacre or become replaced by calcite, silica, or iron-bearing minerals that produce orange-brown colors.

Field identification & locations

Identify by shell symmetry, hinge/umbo features, growth lines, and any surrounding rock matrix; genuine fossils commonly show mineral-filled cavities or altered shell texture. Common in marine sedimentary rocks worldwide.

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Bioclastic limestone, composed chiefly of calcite (CaCO₃)

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Weathered fossil bone fragment (identification uncertain)

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