Blue John Stone is found nowhere in the world but amongst the rocks of Treak Cliff Hill, Castleton and exists in only two caverns: Treak Cliff Cavern and Blue John Cavern.
This mineral, a colour banded form of fluorspar, has been prized for many hundreds of years. Vases found amongst the ruins of Pompeii are thought to be made from Blue John stone. The mineral was much in demand in the 18th century for ornamental vases and columns in some of the finest houses in Britain, most notably Chatsworth, home of the Duchess of Devonshire.
The most substantial veins were worked out so that larger pieces are no longer made. The origin of the name 'Blue John' is thought to have come from the French 'bleu et jaune', meaning 'blue and yellow'.
Treak Cliff Cavern is one of only two working Blue John Stone mines in the world and extracts approximately 0.25 tons per year. The stone is now used for small decorative objects and jewellery, and can be purchased from jewellers and craft shops in Castleton and selected other outlets around the Peak District.
