A stunning example of an iridescent ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The matrix measures 147 mm (5.8 inches) wide and contains a complete ammonite that measures 85 mm, which is a good size for this species. The shell 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 subtle iridescence with the colours changing as the viewing angle changes with green and purple colours present and a pearlescent sheen. The holes in the fossil were caused by natural boring by modern shellfish when the rock was exposed on the seafloor.
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 415 grams. 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.