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Blue John (also known as Derbyshire 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 .
Entrance to Blue John Cavern. The cavern takes its name from the semi-precious mineral Blue John, which is still mined in small amounts outside the tourist season and made locally into jewellery. The deposit itself is about 250 million years old. The miners who work the remaining seams are also the guides for underground public tours.
Treak Cliff Cavern is a show cave near Castleton in Derbyshire, England. It is part of the Castleton Site of Special Scientific Interest [4] and one of only two sites where the ornamental mineral Blue John is still excavated (the other is the nearby Blue John Cavern). [5]
Blue John Gap a mine, one of only two in the world where the beautiful and rare Blue John mineral is found. The Romans created the mine and, in the process, their shaft intersected into the great water-worn caves of the underworld.
Blue John or Bluejohn may refer to: Blue John, Kentucky, United States; Blue John (mineral), a form of fluorite mined in Derbyshire, England; Blue John Cavern, a cavern in Castleton, Derbyshire where fluorite is mined; Bluejohn Canyon, a canyon in Utah, United States, site of the Aron Ralston accident; Blue John, an album by organist John Patton
Pages in category "Blue John (mineral)" The following 5 pages are in this category, out of 5 total. This list may not reflect recent changes. * Blue John (mineral) B.
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The mineral Blue John is now scarce, and only a few hundred kilograms are mined each year for ornamental and lapidary use. Mining still takes place in Blue John Cavern and Treak Cliff Cavern. [26] Recently discovered deposits in China have produced fluorite with coloring and banding similar to the classic Blue John stone. [27]