A stunning and large example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The matrix measure 85 mm (3.35 inches) across and the ammonite measures 42 mm (1.65 inches). The shell sits in the original limestone matrix in which it was found, which 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 rainbow iridescence with flashes of red, yellow, green, and copper that appear as the viewing angle changes. The colours on this one are fantastic and are some of the best we've seen.
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 200 grams.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection.