About this image
Treak Cliff consists of two distinct series of caverns. The outer series was discovered by lead miners in the eighteenth century, and contains some attractive beds of the semiprecious mineral, Blue John. The name Blue John derives from the French Bleu Jaune meaning Blue Yellow. It is a form of fluorite and was discovered as miners were exploring the cave systems of Castleton for lead. Chemically, Blue John is calcium fluoride (CaF2) which has been coloured by films of oil deposited on the crystals millions of years ago. Although it is known as fluorite the old miners, referred to it as fluor spar (sometimes spelt fluorspar). Fluorite often forms in cubic and octahedral crystals and is usually grey, yellow or purple in colour. Fluorite used to be mined mainly for iron smelting but now has many other uses including toothpaste. The form of fluorite unique to Castleton is banded purple and yellow or grey and is known as Blue John. Banded Blue John fluorite has been worked into ornaments since 1750 and there are about 14 categories of banding patterns. Blue John has been prized for ornaments and jewellery and it can be found in many of the best building such as Windsor Castle, the White House and the Vatican. Examples can be seen in Derby Museum and Chatsworth House. The inner series of caves at Treak Cliff, discovered in 1926, contains one of the best displays of stalactites in Castleton. It is called Aladdin's Cave. From this chamber a passage leads into Fairyland, a circular chamber containing a series of stalactites looking very much like carrots seen from below ground. From Fairyland, the passage leads into the Dream Cave. Here, many of the formations have been given names. There is the Elephant, the Crucifix, and many more besides. The longest stalactite here is nearly four feet in length and underneath it is a stalagmite about a foot high, only 1.5 inches away from it. It will take over a thousand years at the present rate of growth before they join up. The next chamber is called the Dome of St. Pauls; nearly 40 feet high, it presents a fascinating spectacle of colours in the stalactite draperies adorning the walls. In 1923 a small cave close to the surface was discovered, containing the remains of two bronze age humans. By 1934 paths and lighting had been installed and the following year Treak Cliff was again opened to the public.