Sterling silver blue john marcasite pearl frog brooch m295 this uniquefrog brooch has been crafted from sterling silver and set with stunning cabachonsof blue john the blue john stones have been surrounded by sparkling marcasite and seed pearls which give the piece a vintage feel 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 yo