Marie Curie used pitchblende ore from Jáchymov to isolate the element radium, a decay product of uranium. Until World War II, uranium was mined primarily for its radium content; some carnotite deposits were mined primarily for the vanadium content. Sources for radium, contained in the uranium ore, were sought for use as luminous paint for watch dials and other instruments, as well as for health-related applications, some of which in retrospect were certainly harmful.