Uraninite is the mineral name for the uranium ore historically called pitchblende.
Uraninite is a radioactive uranium oxide whose idealized chemical formula is UO₂, although natural specimens commonly contain oxygen in varying amounts and impurities such as thorium, lead, and rare earth elements. Its name reflects its uranium content, while “pitchblende” describes the mineral’s pitch-black appearance and resinous to submetallic luster.
The mineral became especially important after uranium’s discovery in the eighteenth century and the identification of radioactivity in uranium minerals during the nineteenth century. Uraninite from Joachimsthal, now Jáchymov in the Czech Republic, helped provide material for early studies of radioactive elements. Marie and Pierre Curie investigated pitchblende residues and discovered polonium and radium.
Uraninite is a major uranium ore, but other uranium minerals, including carnotite and coffinite, can also be economically important. Because uraninite is strongly radioactive, specimens require careful handling and should not be treated as ordinary decorative minerals.