Blue john 9ct gold brooch 50a55m054 this exquisite brooch boasts an unmissable oval shaped cabochon blue john stone that has been sourced directly from treak cliff cavern in castleton the stone has been set within a 9ct yellow gold base with an elegant frilled edge with open detailing 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 stunning pieces of jewellery