Blue John Cavern and Blue John Mine, Castleton
Of the fourteen distinct veins of Blue John, which is a unique ornamental mineral, no less than eight are found in the Blue John Cavern and Blue John Mine, where varieties known as 5-vein and 12-vein are still mined and worked.
A mecca for geologists and tourists alike, the Blue John Cavern and Mine owes more to the might of nature than man, and visitors actually follow the former course of a turbulent underground river, which sculpted its passages and chambers. Several impressive caverns were ground out by vast whirlpools, as evidenced by their swirled, domed roofs, and in one of them a 20-ton limestone boulder still balances – on a mere eight square inches of its surface – where it was dropped by the waters 80,000 years ago. The dried-up river bed is paved now, its many twists and turns and the 241 Pothole Steps qualify visitors for some spectacular underground scenery, all floodlit.
Those who came in the 1840s, paying an entrance fee of two shillings – or for five shillings for a party of four – could pay the guide an extra fee to have the caverns illuminated by Bengal lights, a type of firework. Magnesium wire supplemented candle power for visitors in late Victorian times, when the mine entrance was just a door in the hillside.
Wireless, Radium and Rumours
Various strange activities have taken place inside the hill; in 1922 a 50’ aerial was rigged up across one chamber in an early wireless experiment, when signals were picked up in Cornwall. During the last War the Blue John Cavern became a laboratory for scientists from Christie Hospital in Manchester, being considered the safest place for them to continue their research with radium in pursuit of a treatment for cancer. Their work became know as the Derbyshire Experiment. The scientists were teased with rumours that the caverns were littered with skeletons of ancient Britons, forced to mine Blue John for their Roman masters.
There is a strong tradition of Roman activity in the highest level of the mine, but it was left to seventeenth-century miners to discover the lower cave system and rich veins of Blue John. Displayed on the Roman level, amongst other old mining equipment, are ventilation bellows once worked by young children for sixpence (2.5p) per 12-hour day, working every day but the Sabbath. Throughout the mine are tight apertures where none but children could have pushed out small trolleys of ore.
Completely worked out now is the Bull Beef vein, the rarest and thus most expensive Blue John, with its rich burgundy banding. It was used in one of the Peak’s most beautiful treasures, the tazza vase at Chatsworth House, and a specimen of Bull Beef is preserved in the shop at the mine entrance. Ornamental work nowadays utilises the smaller pieces of stone which bygone miners could afford to overlook when supplies were plentiful. Much Blue John has been retrieved from their old waste, not large enough to make the vases and chalices of old, but not lacking in quality for beautiful jewellery and small ornaments.
Sparkling Chambers and Cascades
One well-illuminated vein of Blue John can be seen in situ in a sparkling chamber known as Lord Mulgrave’s Dining Room; in another corner is a tantalising glimpse across Mirror Lake towards an entrance to the beautiful secret Organ Chamber. An abundance of fossils projects from the multi-coloured walls of Grand Crystallised Cavern, whilst in another section lies a vast bed of thousands of 330-million year old crinoid fossils, aptly nicknamed Derbyshire Screwstone. Petrified flowstone cascades decorate lofty passages linking the network of chambers, the deepest of which, and one of the largest in England, is the rusty-coloured Variegated Cavern. An underground stream gushes into this cavern, whilst the seepage of less hurried waters has draped one recess with a ghostly stalactite of exceptional rarity.