Blue John Bracelet Single Stone Oval Foxtail Silver. B758. This mesmerising bracelet comes from our Foxtail collection and boasts an unmissable oval shaped piece of cabochon Blue John that has been sourced directly from Treak Cliff Cavern in Castleton. The Blue John stone is set on the stunning sterling silver foxtail chain that is completed by a strong magnet 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 in these stunning pieces of jewellery. You can find other matching Blue John jewellery and other Blue John bracelets on our website. Sterling Silver and Blue John.