Each Raven XII B has its own unique ammonite fossil.

Ammonites are an extinct group of marine animals whose fossils are flat spirals that scientists use to identify specific geological time periods. They were probably related not to the nautilus, as one would expect, but to the octopus and squid.

The ammonite Eppler has chosen for Raven XII B is a stunning iridescent fire opal from Madagascar. These fossils date back over 100 million years. They have been polished to a brilliant shine and get their iridescent quality from light passing through the various layers of aragonite, a calcium carbonate mineral, that formed during the lifetime of the ammonite.