fossil

Fossil oyster shell

Fossilized bivalve, likely Ostrea or Crassostrea; calcite (CaCO₃) shell

AI-generated identification · may be incorrect

Irregular, thick shell fragment with layered tan-brown weathering and gray internal patches; typically calcitic, hardness ~3 Mohs, dull to slightly pearly luster, low cleavage, and specific gravity ~2.6–2.8. The ribbed or laminated shell texture and curved cavity are characteristic of oyster valves.

Identified August 14, 2026More fossil →

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Physical properties

Formation & geological history

Formed when a marine oyster shell was buried in sediment and mineral-preserved or recrystallized, commonly during the Cenozoic or Mesozoic; exact age requires its collecting locality and matrix. It is a biogenic sedimentary fossil rather than an igneous or metamorphic rock.

Uses & applications

Primarily a teaching, display, and collecting specimen; fossil shells may also be used in decorative pieces. Comparable common specimens generally have modest commercial value.

Geological facts

Oyster shells are composed mainly of low-magnesium calcite and may preserve growth layers, attachment scars, and the original hinge area. Acid will usually produce vigorous effervescence on a fresh calcite surface.

Field identification & locations

Look for a curved, thick, layered shell wall, hinge structures, growth bands, and possible attachment scars; distinguish it from ordinary limestone by its organized shell architecture. Common in marine sedimentary deposits worldwide, especially former shallow seafloors.