WORLDWIDE AMMONITE FOSSILS FOR SALE AND STUDY. AMMONITES ENTERED AT THE DEVONIAN PERIOD, 400 MILLION YEARS AGO! These FOSSILS were MOLLUSKS that died out about 65 mya. Their shells were composed of Aragonite, a carbonite mineral, which reverts to Calcite over millions of years, some shells were even replaced with PYRITE. Orginally named after AMMON, an Egyptian God of Life. These FOSSIL AMMONITES are from all over the world and will be a great conversation piece in your home, office, or collection. AMMONITES come in all sizes, types, and colors, as you will see from the following pages. CLICK ON PICTURES FOR VIEWING THESE SELECTIONS.