Here is a bed of the ammonite Arnioceras preserved in calcite crystal and iron pyrite. The centres of the ammonites are preserved in calcite but the body chambers (the part of the shell the animal lived in) have been filled in with the pyrite. The local collectors call this ‘Gold Stone’ for obvious reasons.
Arnioceras is one of the most common ammonites in the Lower Lias of Dorset.