Sterling Silver Blue John Oval Signet Ring, R031. This Blue John and sterling silver ring has been expertly hand cut and crafted within our own workshops, featuring an oval piece of Blue John sourced directly from Castleton in Derbyshire, the gemstone is set into a raised oval shaped top. This ring is perfect for every day wear. Dimensions: Blue John: 11mm 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.