Surrounded by the rolling green hills of Hope Valley in Derbyshire's high peak district, lies the pretty little village of Castleton. Since Roman times this picturesque area has been associated with the mining industry - then it was lead, but for the past 250 years it has became famous for the mining of Blue John Stone, and remains only one of two places in the world where mining continues. Over a two-year period approximately 1.5 tons of Blue John are extracted from the Treak Cliff Caverns.
From the village, Treak Cliff Hill rises steeply to some 450ft (136.4m) high, and is about two-thirds of a mile in length by roughly the same dimensions wide. The cavern complex can be divided into two areas, the 'Older Series' and the 'New Series'. When the first Blue John mine was established in the mid-18th century it was called Millers Mine, presumably taking its name from the man who first discovered the veins of the rich mineral deposit (Fluorspar). This has since become known as Treak Cliff Cavern and, by 1765, there were 16 separate Blue John mines opened on this hillside. There are around 40 veins (different patterns of colour-banding ranging from deep blue-black, through various shades of purple and blue, to pure white) of Blue John, creating unique pieces of jewellery, ornaments, bowls and vases. One of the finest veins in Treak Cliff is still referred to as 'Millers Vein'.
The Old Series caverns were worked until the beginning of the 20th century, albeit on a much reduced scale, and then far more extensively during the First World War when the fluorspar was used in blast furnaces. In 1926 a range of new caverns was discovered, set much deeper into the hillside, but no new deposits of Blue John stone were found. What the miners did see was a fantastic display of multi-coloured stalactites resembling a magical grotto, with make-believe sparkling palaces and glistening crystal waterfalls. These caves formed by limestone were appropriately named, Aladdins, Fairyland and the Dream Cave. Mining activities ceased about this time, and by 1935 Treak Cliff Caverns were opened to the public, with limited mining being re-commenced after the Second World War.
A tour of the caves can be a damp, dark and spooky experience, but the rewards are well worth it. Passing through the Old Series, where various veins of Blue John are pointed out, and a gruesome story told of 4,000 year old skeletons being found, the most spectacular part of the tour begins at Aladdins Cave. Hundreds of stalactites, stalagmites, helictites and encrustrations provide an unbelievable feast for the eyes.
The transformation from mineral deposit to a beautiful ornament is a very slow and skillful process. Firstly the material is thoroughly dried, then cut to a rough shape with a circular diamond saw, and next it is impregnated with resin to hold it together. Using a lathe and various attachments, the pieces are turned, carefully ground and polished to a high gloss finish. Blue John was extremely fashionable during the 18th century, and was widely used in the decoration of stately homes and churches before coming into more general use in the form of ornaments and jewellery. Today the stone continues to be mined on a regular basis from Treak Cliff Caverns, but the more substantial veins have been worked out, so the Blue John is crafted into smaller decorative objects and jewellery.