Pitchblende is an amorphous form of the crystalline uranium oxide mineral, known as uraninite. It is one of the primary mineral ores of uranium. Three chemical elements were discovered in pitchblende: radium and polonium, by the French scientists Pierre and Marie Curie in 1898, and uranium, by the German chemist Martin Klaproth in 1789. The mineral contains more than 50% uranium. The term "pitch" was used as the mineral is black in color like pitch, and "blende" was derived after the German miners, who believed that the mineral is composed of different minerals which are blended together.
Crystals of pitchblende are usually cubic, occasionally dodecahedral. Pitchblende has conchoidal to uneven fractures, submetallic to dull luster, a brownish black streak, and opaque appearance. The specific gravity of pitchblende varies from 6.4 to 10.6, and its hardness ranges from 5 to 6.
Pitchblende is commonly associated with secondary uranium minerals, in addition to uraninite. Deposits of pitchblende are observed in the Northwest Territories and Saskatchewan in Canada, England, the Czech Republic, Congo, New Mexico, Montana, Colorado, Arizona and Utah in the United States.
Pitchblende contains small quantities of radium, as a radioactive decay product of uranium. It also contains small amounts of the lead isotopes 206Pb and 207Pb, which are the end products of decay of the uranium isotopes, such as 238U and 235U respectively. Very small quantities of helium are also present in the pitchblende, due to alpha decay.