Sterling silver blue john marcasite heart locket necklace p2151 this vintage style locket features a highly polished cabochon of rare blue john stone sourced directly from treak cliff cavern in castleton this is set in the centre of a patterned sterling silver open framework accented with sparkling marcasite gemstones perfect for keeping someone close to your heart made with sterling silver and includes an 18 inch silver chain all our blue john jewellery is designed and crafted within o