Blue John Necklace Oval Rope Edge Medium Silver. P251. This simple and stylish necklace boasts an unmissable cabochon oval shaped piece of rare Blue John stone that has been sourced directly from Treak Cliff Cavern in Castleton The stone is placed within the centre of a mesmerising sterling silver setting detailed with a twisted rope edge. The pendant hangs gracefully from a delicate sterling silver chain completed by a classic bolt ring clasp for easy wear. All our Blue John jewellery is designed and crafted within our very own workshops in Ashbourne, Derbyshire where a team of skilled craftsmen turn the raw Blue John stone into these stunning pieces of jewellery. You can find other matching Blue John jewellery and other Blue John necklaces on our website. Sterling Silver and Blue John.