AMMOLITE is a recently identified gemstone, formed by irradiant layers that coat some ammonite fossils. Most come from the badlands of Alberta. The process that turns a fossil shell into ammolite is not clearly understood, but the result is similar to opal. Brilliant patterns of colour occur when tiny spherules on the surface split white light, in the same way a rainbow does. The Mesozoic Era saw the evolution of many forms of ammonite, most of which declined in the late Cretacious, along with the dinosaurs.