Uranium Uranium was discovered in the 1700's in the coal mines of bohemia and Jachlovikna. Uranium's atomic number is 92, its Symbol is U and the atomic mass of uranium is 238.0289. Miners called it Pechblende meaning, Pechblende, from the German words pech, which means either pitch or bad luck, and blende, meaning mineral Uranium's first full analysis was done on 1789 by Martin Klaproth, a self-taught well educated german chemist. Klaproth, having extracted from pitchblende what he called 'a strange kind of half metal' (he had only isolated its oxide), he resisted the temptation to give his own name to the new element, which was quite customary at the time. Wi