Polished Fossil Ammonite Cretaceous Period, 145-65 million years B.P. A Cleoniceras sp. ammonite polished through parts of the shell to reveal some of the calcite preserved inside, showing the dividing gas chambers known as suture patterns where the chambers meet the surface giving a zigzag pattern; remains of opalescence at centre to both faces. 170 grams, 90 mm (3 1/2 in.). From Madagascar. From a Lincolnshire, UK, collection. [No Reserve]