The Blue John Cavern is one of the four

show cave A show cave—also called tourist cave, public cave, and, in the United States, commercial cave—is a cave which has been made accessible to the public for guided visits. Definition A show cave is a cave that has been made accessible to ...

s in

Castleton, Derbyshire Castleton is a village and civil parish in the High Peak, Derbyshire, High Peak district of Derbyshire, England, at the western end of the Hope Valley, Derbyshire, Hope Valley on the Peakshole Water, a tributary of the River Noe, between the Da ...

, England. The others are Peak Cavern, Treak Cliff Cavern and Speedwell Cavern.

Description

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 Jewellery (or jewelry in American English) consists of decorative items worn for personal adornment such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the ...

. The deposit itself is about 250 million years old. The miners who work the remaining seams are also the guides for underground public tours. The eight working seams are known as Twelve Vein, Old Dining Room, Bull Beef, New Dining Room, Five Vein, Organ Room, New Cavern and Landscape. In 1865, Blue John Cavern was the site of the first use of

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

to light a photograph underground. It was taken by Manchester photographer Alfred Brothers.

Blue John

In the UK Blue John, or "Derbyshire Spar", is found only in Blue John Cavern and the nearby Treak Cliff Cavern. It is a type of banded

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...

. The most common explanation for the name is that it derives from the French ''bleu-jaune'', meaning 'blue-yellow', but other derivations have been suggested.

References

External links

* * {{Derbyshire Places of interest Castleton, Derbyshire Caves of Derbyshire Show caves in the United Kingdom Tourist attractions in Derbyshire Tourist attractions of the Peak District Blue John (mineral) Fluorite mines