Cabine du Jardin deux: Treak and Blue John

Friday 30 August 2013

Treak and Blue John

View across the Hope Valley Castleton Derbyshire from above the entrance to Treak Cliff Cavern

Earlier in August, Toot, the Family Bimbar and I visited the Treak Cliff Cavern in Derbyshire. We had an excellent tour of the cavern led by a knowledgeable and funny guide. He also shared my interest in Banjos and Bluegrass picking!

The Treak Cliff Cavern was started as a mine over three hundred years ago and during more recent mining operations an entrance to naturally occurring limestone caverns was found. The caverns are a major tourist attraction but Blue John is still mined at Treak outside of the main tourist season.

Blue John is a blue and orange banded fluorite mineral. It is extremely decorative and has been used for jewelry probably since Roman times. The use of Blue John for the manufacture of cups, bowls and tops for high class furniture was particularly popular with the gentry in the 18th and 19th centuries. There are magnificent examples of worked and turned Blue John artifacts at the nearby home of the Duke of Devonshire, Chatsworth House. Blue John is not easily worked as it contains many potential lines of fracture, so in order to turn a Blue John bowl, the mined mineral has first to be impregnated with resin.

Blue John Vein

The mineral veins of Blue John were formed in the Derbyshire Peak District during the Carboniferous Period. The minerals were deposited in veins by layers of crystals precipitating from hot fluids coating the walls of fractures, caves, and other cavities. The Blue John Fluorite is often found associated with Dog Tooth Calcite Crystals and fossil crinoidal lilies.

I purchased a piece of Blue John with an integral section of crinoid lily stem from the Treak Cavern Shop.

My Purchase

The Treak Cliff Cavern is also famous for its coloured flowstone, stalactites and stalagmites. For those that cannot remember, stalactites hang down and stalagmites thrust up from the ground. It is generally accepted that Treak Cliff Cavern boasts the finest stalactites in the Peak District. Nearby the Treak Cliff Cavern are the Blue John Cavern and the Speedwell Lead Mine but in my view Treak is the best to visit.