A stunning example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The piece of thin limestone matrix measures 162 mm (6.4 inches) across and contains a single complete ammonite that measures 62 mm (2.42 inches).
The ammonite is very well preserved and has been prepared out of the rock to reveal the shell, which displays some beautiful subtle iridescent colours that change depending on the angle that the fossil is viewed at. There are flashes of green against a pearlescent background. It weighs 418 grams and has a cut-flat base to allow it to be displayed freely standing.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection. These fossils are preserved in the same way as the more famous Canadian "ammolite", which is turned into valuable gemstones due to the stunning iridescence.