A stunning example of a calcite ammonite fossil of the species Caloceras johnstoni from North Somerset, UK.
The ammonite measures 133 mm (5.26 inches) across, which is huge for this species and not far off as big as they get. It sits in a piece of limestone matrix that measures 240 mm (9.45 inches) wide that has been shaped and backed with a plaster wedge at the base to allow it to stand freely for display. The ammonite is very well preserved with part of the outer whorls missing and has been prepared out of the rock to reveal the detail of the shell, which displays some stunning iridescence, showing a wide range of colours that change as the angle of light changes. There has been some very minor repair to the outer whorl to stabilise a crack in the original matrix.
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 1265 grams.
Around 200 million years old (Hettangian, Early Jurassic), this fossil would make a wonderful addition to any collection.