18ct white gold blue john 033ct diamond round halo ring r898 this enchanting ring boasts an unmissable round piece of rare blue john stone in the centre that has been directly sourced from treak cliff cavern in castleton the stone is set within exquisite 18ct white gold and surrounded by a mesmerising halo of 033ct brilliant cut diamonds that also run down the shoulders of the classic band all our blue john jewellery is designed and crafted within our very own workshops in ashbourne derbysh