Silver Blue John Oval Stud Earrings. E098. These classic stud earrings boast two stunning oval shaped cabochon pieces of rare Blue John stone that have been sourced directly from Treak Cliff Cavern in Castleton. The stones are set within simple sterling silver frames that are completed by post and butterfly fastenings 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 earrings on our website. Sterling Silver and Blue John.