Silver blue john marcasite flower ring r815 this feminine floral sterling silver blue john and marcasite ringfeatures a circular central piece of blue john that has been sourced directly from treak 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