Sterling Silver Blue John Spiral Flower Necklace, P2556. This contemporary necklace features a round hand carved Blue John gemstone sourced from Castleton in Derbyshire, which is set within the centre of a highly polished swirl of sterling silver. This item is supplied complete with and 18 inch sterling silver chain. Dimensions: 12mm x 10mm, Blue John; 5mm x 5mm. All articles purchased from C W Sellors are lovingly and securely dispatched with our elegant jewellery packaging. Matching items are available within this collection.