A stunning example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The matrix measures 210 mm (8.26 inches) wide and the ammonite measures 102 mm, which is large for this species. The shell sits in a piece of limestone matrix that has been shaped and backed with plaster for stability. The ammonite is very well preserved and has been prepared out of the rock to reveal the whole shell. The shell displays stunning iridescence, showing all of the colours of the rainbow that change as the angle of light changes, with green and orange colours dominating. The very centre of the shell is missing, but this does little to detract from this wonderful specimen. It has a cut-flat base to allow it to stand freely for display purposes.
These fossils are highly sought after and very hard to find. They are preserved in the same way as the famous Canadian "Ammolite" ammonites that are turned into valuable gemstones. The fossil weighs 835 grams.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection.