Sterling silver blue john marquise celtic ringr462 this elegant ring features a marquise cabochon hand carved blue john which has been sourced directly from the derbyshire blue john cavern in castleton the highly polished blue john is framed by a unique celtic style band of sterling silver 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 into these stylish pieces of jewel