Silver blue john marcasite oval beaded edge ring r750 this feminine sterling silver blue johnand marcasite ringfeatures an ovalcabochonof blue john stone that has been sourced directly from treak cliff cavern in castleton the striking stone issurrounded by glittering marcasite and framed by a beaded silver design 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 in