Considered one of the most collectible types of Ammonite, Pyritized Ammonite is a Ammonite fossil that has undergone pyritization where Iron Pyrite replaces the Ammonite's shell structure cell by cell. It is a form of fossilization that results in a beautiful shine and gleam as seen in this example. 

Ammonites appeared in the fossil record approximately 240 million years ago during the Triassic period and disappeared around 65 million years ago at the end of the Cretaceous. They were predatory mollusks related to the Nautilus and modern-day Squids.  

Due to the natural formation of these fossils, no two Ammonites will look the same. The Ammonite you receive may not look exactly like the one pictured here, but will have similar characteristics.