Blue john necklace diamond 9ct yellow gold p390 this exquisite necklace boasts a stunning cabochon diamond shaped piece of rare blue john stone that has been sourced directly from treak cliff cavern in castleton the stone has been placed within a mesmerising 9ct yellow gold setting that hangs gracefully from a matching yellow gold chain 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 blu