18ct white gold square blue john 018 carat diamond stud earrings e1334 these unmissable stud earrings boast two stunning square shaped pieces of rare blue john stone that have been directly sourced from treak cliff cavern in castleton the stone is placed within an exquisite 18ct white gold earring setting and surrounded by dazzling 018 carat brilliant cut diamonds creating a breathtaking sparkle all of our blue john jewellery is designed and crafted within our very own workshops in ashbou