Ammonite: 66 Million Years in the Palm of Your Hand

Long before they became polished collector pieces, ammonites were living creatures — coiled-shell cephalopods related to today's nautilus, squid, and octopus — that thrived in the world's oceans for hundreds of millions of years before going extinct alongside the dinosaurs roughly 66 million years ago. Their fossilized shells are among the most recognizable and widely collected fossils in the world.

Our ammonite fossils come from Madagascar, where they're commonly found split into matching pairs — a single fossilized shell sliced and polished on both halves to reveal the internal spiral chambers, called septa, that the animal used for buoyancy control. Many pieces show opalization on the outer shell, catching flashes of rainbow color where the original shell material has been replaced by iridescent minerals over millions of years.

It's worth noting the difference between ammonite and ammolite: ammonite refers to the fossilized shell itself, while ammolite specifically describes gem-grade material with strong, consistent opalescent color — you can read more about that distinction in our Ammolite guide. Ammonite fossils are an excellent entry point into fossil collecting: genuinely ancient, visually striking, and accessible in size and price.

Browse our ammonite fossil pairs and singles, sized well for display, jewelry making, or starting a fossil collection.