Polished Ammonite Shell Fossil Slice, Fossilized Shell Specimen, Sea Shells. Beautiful and rare, these iridescent ammonite fossils are sure to shine in your home. Each is a natural piece of a fossilized shell that lived 200+ million years ago. They make a beautiful addition to any home, office, or decor. This listing is for one (1) Ammonite split in half. Crystals for your collection & sharing with friends.