Discovered in 1913 by Fajans and Göhring, and then isolated in 1934 by Grosse, protactinium is named from the Greek proto + actinium (parent of actinium). The silvery-white metal is extremely rare, very radioactive and highly poisonous. Originally called brevium by its discoverers because of the short life-time of the transition between Th-234 and U-234, a longer-lived isotope was eventually isolated and called protoactinium by Grosse. The name was shortened to its present form in 1949. About 60 tons of pitchblende ore (which contains uranium, radium, and a host of other radioactive elements) yields about 125 grams of protactinium.