Blue John (mineral)
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Blue John is a semi-precious mineral, a rare form of fluorite with bands of a purple-blue or yellowish colour. In the United Kingdom it is found only at Blue John Cavern and Treak Cliff Cavern at Cast
Bowl made from Derbyshire Blue John, on display in Castleton Visitor Centre
French candelabra crafted of Blue John, c. 1860
Vein of Blue John Fluorite in Treak Cliff Cavern
Blue John seams in Blue John Cavern
Blue John Cavern
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The Blue John Cavern is one of the four show caves in Castleton, Derbyshire, England. The others are Peak Cavern, Treak Cliff Cavern and Speedwell Cavern.
Blue John (mineral)
…Spar) is a semi-precious mineral, a rare form of fluorite with bands of a purple-blue or yellowish colour. In the United Kingdom it is found only at Blue John Cavern and Treak Cliff Cavern at Castleton in Derbyshire. During the 19th century, it was mined for its ornamental value, and mining continues on a small…
Entrance to Blue John Cavern