Pitchblende

Pitchblende, a mineral found in Cornwall, Turkey, and other localities, which is interesting as being the chief ore and source of the metal uranium (q.v.). It consists of oxides of this element, possessing the formula U308, but usually contains iron, silica, lead, and other substances as impurities, and is of a black and massive appearance, occurring in brilliant octahedral crystals (specific gravity, 9-35).