You’re standing outside Treak Cliff Cavern, one of only two places in the world where Blue John is mined. (the other is Blue John Cavern, also nearby). Blue John is a variety of a mineral called fluorspar, composed of calcium fluoride (CaF2). Fluorspar comes in a range of colours, but Blue John is characterised by bluish purple with white or yellow banding. Its colour and translucency have made it popular for creating ornaments or jewellery – but these qualities have also been exploited to create decorative ‘windows’, akin to stained glass.
The window above was made by Castleton-born John Tym. It is made in three pieces, each containing thin slices of Blue John glued onto glass. It was commissioned in the late 1800s for Birchfield Lodge, Hope, where it remained until 1983. It is now reframed in a light box and on display at Buxton Museum and Art Gallery.
In 2016, inspired Tym’s work, Buxton Museum comissioned a new Blue John window, the first for 150 years. It contains polished slices from most of the named mineral veins in the Castleton mines, including specimens from the collection at Buxton Museum. The inspiration for the design is the view from Treak Cliff Cavern, looking east along the Hope Valley.
Take a moment to look out over the valley now. Can you match any of the window features to the landscape before you?
This window was designed by artist Caroline Chouler-Tissier with the help of 38 children from the Buxton Artbox Artclubs and staff at Treak Cliff Cavern led by Katherine Darlington. It was assembled by Stephen Parsonson and Rob Ramwell at Classic Glass.
John Tym (1829-1901) was born in Castleton and is first listed in the Derbyshire directories of 1855 as a “spar worker and museum” alongside his father who was “guide to the Blue John mine”. In 1876 Tym was hired as curator at J Rooke Pennington’s new museum in Castleton, entered via Tym’s Spar and Marble Shop. After the contents of the museum were put up for sale in 1883 Tym moved to the Stockport Museum where he collected mineral specimens from around the country. A large, arched window by Tym can be seen at Vernon Park, Stockport.