A stunning example of a calcite ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The ammonite measures 115 mm (4.52 inches) across, which is large for this species, and sits in a piece of limestone matrix that has been shaped around the ammonite 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. There is also a very unusual natural geological fault line running through the ammonite, which will have occurred at some point in the 200 million years when this fossil was buried underground. This adds an interesting geological feature to this fossil and makes it a real one-off specimen.
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 120 grams.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection.