Blue John Cavern
| Blue John Cavern | |
|---|---|
 Entrance to the Blue John cavern |
|
| Location | Castleton, Derbyshire |
| Geology | Blue John |
| Number of entrances | 1 |
The Blue John Cavern is one of the four show caves in Castleton, Derbyshire, England. The cavern, which takes its name from the semi-precious mineral "Blue John" or "Derbyshire Spar", is still mined for the mineral outside of the tourist season. The small amounts taken are turned into locally-made jewellery. 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.
The cavern was featured on the 2005 TV programme Seven Natural Wonders as one of the wonders of the Midlands.
Contents |
[edit] Etymology
The commonest theory for the name Blue John derives from the French bleu-jaune, meaning 'blue-yellow'. Large quantities of Blue John was sent to France in the late 18th century where it was used for gilding by French Ormolu workers during the reign of the Louis XVI (1774 – 1791). However, the French craftsmen were emulating ormolu ornaments already created by Matthew Boulton of Birmingham, who around 1765 was already calling the stone 'Blew John'.
An alternative origin of the name was suggested by John Royse, the lessee of the cavern in 1938. He noted that as an old miners' name for metal-blended stone was "Black Jack", Royse postulated whether the unique blue stone mined in these caverns led it to be known as "Blue John".
[edit] Geology
Blue John is a type of banded fluorite. Although blue fluorite occurs widely throughout Derbyshire, especially around Ashover and Crich, only the blue-purple and white-yellow variety is found in Castleton at Blue John Cavern and at the nearby Treak Cliff Cavern.
Within the UK, blue fluorspars are also found in County Durham (especially Weardale), Cornwall and Wales. Other deposits of banded blue fluorite occur in Nevada, United States, and Southern Iran. Two cups found among Roman grave-goods near the Turkish/Syrian border, on the former Persian-Roman trade route, were made from Iranian blue-yellow banded fluorspar. Two Blue John vases have also been found during excavations at Pompeii. [1]
[edit] Usage
In the 18th century a small local industry began turning vases of Blue John, these could be mounted with ormolu as chimneypiece garnitures. The earliest dated decorative applications of Blue John in Britain are the marble fireplace panels, designed by neoclassical architect and interior designer Robert Adam, that were installed at Kedleston Hall near Derby in 1762. Blue John became such a popular medium for ornamental bases that manufacturer and industrialist Matthew Boulton tried unsuccessfully to obtain exclusive mineral rights for the whole output from the Castleton mines.
Despite small-scale mineral extraction continuing at the Castleton caverns, similar blue and white-yellow banded fluorite is now imported into the UK from China.[2]
[edit] References
- ^ "History of the Blue John Cavern". Official site of Blue John Cavern. http://www.bluejohn-cavern.co.uk/pages/history.php. Retrieved September 2010.
- ^ Graham Hill, John Holman (2000). ISBN 0174482760. Chemistry in context.
