Sterling Silver Blue John Large Cushion Signet Ring, R180. This classic signet-style ring features a hand carved curved square Blue John gemstone, which is inlaid into a thick band of sterling silver. Because the Blue John is inlaid within the metal, this creates a beautiful smooth finish and creates a brilliant shine. Dimensions: Blue John; 13mm x 11mm. Width of band; 4mm. All articles purchased from C W Sellors are lovingly and securely dispatched with our elegant jewellery packaging. Matching items also available within this collection.