A stunning example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The piece of thin limestone matrix measures 77 mm (3.05 inches) across and contains a single ammonite that measures 25 mm (1 inch), making it a small juvenile of this species.
The ammonite is very well preserved and has been prepared out of the rock to reveal the shell, which displays some subtle iridescent colours that change depending on the angle that the fossil is viewed at. There is a pale mix of bronze and copper colours in the shell. It weighs 118 grams.
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.