Sterling silver blue johntoscana side marquise ring r513 this contemporary ring is part of our stylish toscana collection and featuresa marquise shaped cabochon of rare blue johnstone that has been sourced locally from the treak cliff cavern in castleton the stone is framed within a highly polished sterling silver setting with a classic band 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