What is the name of the uranium ore from which Marie Curie extracted radium?

The uranium ore from which Marie Curie extracted radium was pitchblende. Also called uraninite in mineralogical contexts, pitchblende is a dense, dark uranium-rich ore that became central to the Curies’ early radioactivity research.

Curie noticed that pitchblende was more radioactive than its uranium content could explain. She reasoned that the ore must contain additional, undiscovered radioactive substances. In 1898, the Curies announced polonium and radium after chemically separating tiny fractions from the ore.

Extracting radium was extraordinarily laborious. The Curies worked with tonnes of pitchblende residue and used repeated chemical separation and fractional crystallisation. Radium was difficult to isolate because it is chemically similar to barium, so the two elements tended to remain together.

Uraninite is the modern mineralogical name often used for the same uranium oxide mineral, which explains the common quiz mix-up. “Pitchblende,” however, is the traditional term associated with the Curies’ radium experiments and is the standard answer to this historical question.