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