Sterling silver blue john foxtail large oval necklace n494 this uniquenecklace is part of our popular foxtail collection and features a cushion shaped cabochon of rare blue john gemstone sourced from the treak cliff cavern at castleton in derbyshire the stone is framed in intricately woven sterling silver foxtail chain that hangs gracefully around the neck all our blue john jewellery is designed and crafted within our very own workshops in ashbourne derbyshire where a team of skilled craft