BLUE JOHN MINE, a chambered cave in the Main Tor, Derby; about a mile WNW of Castleton. It is entered by steeply descending stairs; contains a chamber, n 60 feet wide and 150 feet high, called Lord Mulgrave's n dining-room; has, further in, another chamber, called the Variegated cavern, and beyond this a profound gulf, overlooked by a rail-guarded ledge; makes a magnificent display of stalactites and crystals; and yields a vast quantity of beautiful spar. It is visited under the direction of guides; and shown with Bengal lights and blasts.

(John Marius Wilson, Imperial Gazetteer of England and Wales (1870-72))