Uranium was discovered in 1781 by Klaproth, a pharmacist in Berlin, from the black mineral pitchblende found in Joachimsthal silver mines. Peligot in France in 1841 proved that what Klaproth isolated from pichblende was uranium oxide and not the metal. Uranium salts were used at that time to manufacture coloured glass before the discovery of its radioactivity in 1896. It became in great demand when its decay product radium was found to cure cancer. The discovery if uranium fission in 1939 was the reason for the manufacture of the first atomic bomb.