| geology = Carboniferous limestone

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Treak Cliff Cavern is a show cave near Castleton in Derbyshire, England. It is part of the Castleton Site of Special Scientific Interest and one of only two sites where the ornamental mineral Blue John is still excavated (the other is the nearby Blue John Cavern).

The cave comprises three sections, the Old Series, discovered by lead miners in the 18th century, the New Series, discovered during blasting in the 1920s, and the New Series Extensions, discovered in 2014. Only the Old Series contains Blue John, but the New Series is well decorated with flowstone, stalagmites, and stalactites. The New Series Extensions are also highly decorated, but are only accessible by experienced cavers. Three human skeletons and flint implements from the Neolithic era were found in a small cave nearby in 1921. Surface streams, on meeting the limestone, percolated through cracks and weaknesses and started to dissolve the limestone to form caverns. The stream that formed the New Series once flowed into the lower end of Winnats Pass, whereas the stream that formed the Old Series lost its headwaters to the predecessor of the modern Odin Sitch as it cut down through soft shales. There is no modern stream in the Treak Cliff Cavern, but percolating water from the cave has been dye-tested and found to emerge at the Russet Well beside Peakshole Water near Peak Cavern in Castleton, taking 13 to 20 hours to travel the distance.

thumb|Stalactites in the New Series

Demand for fluorspar increased during World War I and much ornamental Blue John was extracted for use as flux in blast furnaces and in the chemical industry. In 1921 miners discovered the remains of three human skeletons dated to the Neolithic period in a nearby cave close to the surface. A little later, in 1926, miners blasting with explosives discovered an extension to the natural cavern, a section well decorated with stalactites: the New Series. At current rates of extraction, the find was expected to last for at least ten years. The discovery prompted a visit by the BBC's Countryfile programme later that year.

Ridley Vein

In 2015, another vein of Blue John was discovered close to the tourist route by a miner experimenting with a new method of exploration using a specialist chainsaw. The first new source for 150 years, it was named the Ridley Vein after its discoverer.

New Series Extensions

In April 2014, after 18 months of hard digging, 2 local cavers - Mark Cope and Martin Barnsdall discovered an extension deep underneath 'Dome of St Pauls'.

The extensions start in a small chamber to the side of 'Dome of St Pauls', where in the corner a vertical dig through mud and scree resulted in a twisting 10m deep shaft, called 'Crooked Spire Shaft'. At the end is a small vug of Blue John and Calcite, then underneatha tight squeeze leads to the top of a steeply sloping passage - '2014 Passage', off to the west side is a highly decorated chamber 'Wonder Cave', and small tight squeeze leads to a tiny chamber 'Emilys Cave' (after Marks then newly born daughter).

Another exceedingly tight squeeze leads to another small chamber with a brown flowstone floor and brown stalatites 'Brown River Series'.

Back at '2014 Passage', this descends steeply for about 5m into a large sloping chamber called 'Marbles' as the floor was tricky to walk over. This chamber has a vast amount of water flowing through from the ceiling as it is 20m directly below the tourist cave. In the SE corner of the chamber is a large scree pile with much water flowing through, the scree is thought to originate in the 1926 Passage some 50 to 60m higher. There are 2 avens in the roof of the chamber, only 1 has been climbed to a blockage thought to connect with a chamber underneath the walking route of the tourist cave.

Another squeeze in N side of the chamber leads down to a small chamber 'Measureless to Man'(named after instructions from the owner of Treak Cliff Cavern, Vicky Turner, to find such caves.) This then leads via another small 2m shaft and 3m muddy slope to the current end of the New Series, a tiny chamber where a small trickle of water disappears under a wall.

References

  • showcaves.com
  • theheritagetrail.co.uk