Placenticeras sp. from the Bearpaw Formation, Campanian, Late Cretaceous (83.5-72 MA)
The fossils of Placenticeras ammonites that were found in the fossiliferous sands of Canadian Alberta are considered to be among the most precious in the world due to the fact that they are entirely made up of an organic gemstone called ammolite. Ammolite is the result of the mineralisation of the mother-of-pearl that makes up the shell of this cephalopod, an ancestor of Nautilus. Gorgeous shades of red and green shift on the surface of this iridescent material.