18ct White Gold Blue John Diamond Round Cluster Ring. R1114. This unique 18ct white gold ring features a stunning hand carved cabochon of the finest Blue John stone, sourced directly from Castleton, Derbyshire. Sparkling diamonds (0.09cts) form a delicate halo around the beautiful Blue John. The perfect engagement ring featuring a rare British gemstone.  At C W Sellors, we have an expert team of gemstone and diamond specialists who handpick and grade each jewel to meet our high standards and a team of talented in house designers who combine their talents to bring you our exclusive Precious Gemstone collection. You can find other matching Blue John and diamond pieces online and in store. All articles purchased from C W Sellors are lovingly and securely dispatched with our elegant jewellery packaging.