Blue John

Blue John is a banded variety of the mineral Fluorite only ever found at Mam Tor ‘the shivering mountain’ at Castleton, Derbyshire, UK

The Romans first mined & prized this stone making elaborate vases and urns from it.

The name "Blue John” is though to come from the French "Bleu, Jaune” or "Blue, Yellow” which describes the banding of the stone.