fossil

Fossil brachiopod in iron-rich matrix

Brachiopoda fossil; matrix likely limonite/goethite with carbonate shell

AI-generated identification · may be incorrect

The specimen shows a ribbed, bilaterally symmetric brachiopod shell surrounded by brown-black earthy iron oxides and pale carbonate material. Shell calcite is Mohs 3–4, with dull to waxy luster; iron oxides are commonly harder and denser, with no consistent crystal form visible.

Identified September 10, 2026More fossil →

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Physical properties

Formation & geological history

Brachiopods were marine filter-feeders whose calcitic shells were buried in seafloor sediment and later mineralized or coated by iron oxides during diagenesis and weathering. Exact geological age cannot be determined from the image; brachiopods range from Cambrian to Recent, with many collectible examples Paleozoic.

Uses & applications

Primarily a collector, educational, and display specimen; it has no practical construction or jewelry use. Value depends on species, preservation, locality, preparation, and documented provenance.

Geological facts

Brachiopods resemble clams but have different symmetry: each shell valve is symmetric around its own midline, unlike bivalves. The dark brown coating likely reflects limonite/goethite staining or replacement.

Field identification & locations

Look for the characteristic ribbed two-valved shell, hinge, and bilateral symmetry; dilute acid may fizz on exposed calcite, though testing can damage it. Common fossil localities include Paleozoic marine limestones worldwide.