A stunning example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The matrix measures 82 mm (3.2 inches) across and the ammonite measures 20 mm (0.8 inches), making it a small juvenile of the species. The ammonite sits in the original limestone matrix in which it was found that has been shaped and has a cut-flat base to allow it to be displayed freely standing. The ammonite is very well preserved and has been prepared out of the rock to reveal the shell, which displays some beautiful iridescence that causes the colours to change as the viewing angle changes. There are deep green, orange, and red hues in the shell, making it about as close to rainbow coloured as these fossils get. The fossil weighs 112 grams.
These fossils are highly sought after and hard to find, especially complete examples like this one. They are preserved in the same way as the famous Canadian "Ammolite" ammonites that are turned into valuable gemstones. These fossils make great unusual gifts and each one is totally unique.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection.