Noun
A mineral consisting chiefly of uranium oxide with some lead, thorium, etc., occurring in black octahedrons, also in masses with a pitchlike luster; pitchblende.
Source: Webster's dictionaryDiscovery details Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite sample. Source: Internet
They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Source: Internet