What is Derbyshire Blue John?
Blue John Calcium Fluoride Mineral
A rare type of fluorite known as Derbyshire Blue John, this calcium fluoride mineral can only be found close to the village of Castleton in Derbyshire.
The stone's blue, purple, yellow and white colour comes from films of oil that fell on the crystals many millions of years ago.
The Blue John vase in our photo is on display in the Natural History Museum London. Photo; Stone Mania ©. The image is clickable and redirects to the original non-compressed photo.