Silver blue john 10mm ball stud earrings e1346 these simple and stylish stud earrings feature twopolished 10mm roundrare blue john stones that have been sourced directly from treak cliff cavern in castleton the stones are set on sterling silver posts and fastened by classic 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 stu