Marie Curie is remembered for her discovery of radium and polonium, and her huge contribution to finding treatments for cancer. In 1898, the Curies published strong evidence supporting the existence of the new element – which they called radium – but they still had no sample of it. Pitchblende is an expensive mineral because it contains valuable uranium, and Marie needed a lot of it. In 1902 Marie isolated radium (as radium chloride), determining its atomic weight as 225.93.

Source: Marie Curie