Ammonites

Pyritised ammonite

Little pyritised ammonites from Gloucestershire in England, and around 190 million years old. They are a mixture of species, including Cheltonia, and vary slightly in size. The pyritisation is a natural process where the replacement is by iron pyrite instead of - say - quartz or calcite. The result is a silvery to brassy metallic sheen. 

1-2cm