Silver blue john marcasite round ring r821 this feminine sterling silver blue john and marcasite ringfeatures a circular central piece of blue john stonethat has been sourced directly fromtreak cliff cavern in castleton the striking stone issurrounded by intricate petals with tiny pieces of marcasite at their hearts 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 i