The ammonite shell has been ground away and the cast of the inside of the shell, formed from calcite and sediment, has been polished to show up the suture lines. These complex patterns were made where the chamber walls met the inside of the shell itself and can therefore only be seen when the shell is removed.
The ammonite was found in Horn Park Quarry near Beaminster. The quarry is the smallest National Nature Reserve (NNR) in Britain, being just one acre or 0.32 hectares in size. It was once a working quarry but it is no longer and the remaining outcrop is protected by a fence. There is no collecting other than for scientific and educational purposes. A section of the fossil beds has been stripped back and protected from the weather by a removable cover. To arrange a visit, contact the Senior Reserve Manager on 07899 731404.
Find out more about ammonites on the molluscs pages.