THE mineral Blue John Stone is a unique banded form of fluorspar, a white or colourless mineral, sometimes fluorescent and often tinted by impurities, found in veins and as deposits from hot gases.
It is used in the manufacture of glass, enamel and jewellery, and is also the chief ore of fluorine.
Mining of the stone in Derbyshire began in the 18th century with the local folk coining the name of Blue John.
It is believed it was originally given its name from the French “bleu et jaune” – blue and yellow.
Treak Cliff Cavern is a spectacular natural cavern with amazing formations of stalactites.
It is one of only two working Blue John mines in the world, providing Blue John for jewellery and ornaments, much of which is hand-crafted on site.
The cavern is a Site of Special Scientific Interest.