A stunning example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The matrix measures 122 mm (4.8 inches) across and contains a partial ammonite that measures mm, which is large for this species. The shell sits in the original limestone matrix in which it was found that has a cut-flat base to allow it to stand freely for display. The ammonite is very well preserved and has been prepared out of the rock to reveal the shell. The shell displays some beautiful multicoloured iridescence with different green, blue, and copper that appear as the viewing angle changes. This one really has spectacular colours. There is also an unusual geological fault running through the ammonite creating a unique appearance with the white line across the colourful shell.
These fossils are highly sought after and very hard to find, especially complete like this. They are preserved in the same way as the famous Canadian "Ammolite" ammonites that are turned into valuable gemstones. The fossil weighs 340 grams.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection.