Sterling silver blue john long marquise celtic necklace p1391 this elegant necklace features hand carved blue john that has been sourced directly from the derbyshire blue john cavern in castleton the highly polished blue john marquise is framed within a unique sterling silver celtic design with the pendant being presented on a 18 sterling silver chain all our blue john jewellery is designed and crafted within our very own workshops in ashbourne derbyshire where a team of skilled craftsmen