Blue John is only found beneath Treak Cliff Hill, near Castleton, and gets its name from its distinctive colour. It is now only mined in two caverns - Treak Cliff Cavern and Blue John Cavern.
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Beautiful landscapes
Stop in Castleton and you can get below it all: four large natural caverns are open to the public. They were made more expansive by mining that began here during the time of Roman occupation.