fossil

Silicified fossil shell, likely fossil oyster or clam

Silicified bivalve fossil; shell originally aragonite/calcite, partly replaced by chalcedony (SiO₂)

AI-generated identification · may be incorrect

Tan-brown, irregular layered shell form with a pale waxy translucent interior and rough matrix. Chalcedony has Mohs hardness about 6.5–7, vitreous-to-waxy luster, cryptocrystalline structure, and no visible cleavage; surrounding material appears sedimentary and iron-stained.

Identified August 15, 2026More fossil →

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Physical properties

Formation & geological history

A marine bivalve was buried in sediment, then its shell was mineralized or partly replaced by silica-rich groundwater. Exact age cannot be determined from the image; such specimens range from Paleozoic to Cenozoic deposits.

Uses & applications

Primarily a collecting, educational, and decorative specimen; polished sections may be used as curiosities, but it has little industrial or jewelry use.

Geological facts

The preserved shell architecture and growth layers distinguish it from ordinary chert. Orange coloration commonly comes from iron oxides or hydroxides such as hematite and goethite.

Field identification & locations

Look for bilateral shell symmetry, growth lines, hinge features, and a sharp boundary between fossil and matrix; a steel file should not easily scratch the pale silica-rich area. Common in fossil-bearing marine sedimentary formations worldwide.