fossil

Polished ammonite fossil

Ammonoidea; commonly Jurassic or Cretaceous ammonite, often preserved in calcite or aragonite

AI-generated identification · may be incorrect

Fossilized, coiled cephalopod shell with visible chambers and sutures; typically calcite-rich, Mohs hardness about 3–4, earthy to golden-brown color, dull to waxy or polished luster, and curved chambered structure.

Identified September 7, 2026More fossil →

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Physical properties

Formation & geological history

Ammonites were extinct marine cephalopods whose shells accumulated in seafloor sediments and fossilized through mineral replacement or infilling. Most commercial specimens are roughly 66–201 million years old.

Uses & applications

Used as decorative objects, educational fossils, and collectibles; high-quality iridescent ammonites may be cut for jewelry and ornamentation.

Geological facts

The spiral reflects the animal’s chambered shell, while the intricate dividing lines are sutures. Ammonites are excellent index fossils for correlating Mesozoic marine rocks.

Field identification & locations

Identify it by the planispiral coil, repeated chambers, and ornate sutures; common sources include Morocco, Madagascar, Canada, Germany, and the United Kingdom. Avoid acids and prolonged soaking, which can damage calcite or coatings.