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pitchblende(pĭch`blĕnd'), dark, lustrous, heavy mineral, a source of radium and uranium. Largely natural uranium oxides, triuranium octaoxide (U3O8) and uranium dioxide (UO2), it usually contains some lead and variable amounts of thorium and rare-earth elements. It is massive in form, frequently with a botryoidal, or grape-cluster, appearance, and has a variable but high specific gravity. Pitchblende is greenish, brownish, or black in color, with a pitchy to submetallic luster. The uranium yield is from 50% to 80%. Uraninite, a closely related ore richer in uranium (uranium dioxide), commonly crystallizes in the cubic system. It yields 65% to 80% uranium and has a specific gravity somewhat higher than that of pitchblende. The color range is from deep black to brown. Both ores occur as primary constituents of quartz veins and with other metals. They supply radium and polonium in addition to uranium. Although the ores occur in small quantities throughout the world, the Great Lakes region of Canada, Congo (Kinshasa), the Czech Republic, the Colorado Plateau, Australia, and South Africa are the major sources.
(nasturan), a variety of uraninite occurring as massive and colloform aggregates that contain variable quantities of UO3 (predominant constituent) and UO2. Admixtures include radiogenic lead, calcium, sometimes rare-earth elements of the yttrium subgroup, and up to 2–3 percent H2O. Pitchblende’s crystal structure generally corresponds to that of uraninite; however, pitchblende is converted to an amorphous state when UO3 dominates. An opaque black mineral with a pitchlike luster, it has a hardness of 4—6 on Mohs’ scale. Its density, depending on the UO2: UO3 ratio, varies from 6,000 to 9,200 kg/m3. The mineral is highly radioactive.
Pitchblende is one of the most widely occurring uranium minerals. It is found in complex hydrothermal ore deposits in association with tin and tungsten minerals, as well as with arsenides and sulfarsenides of cobalt, nickel, and iron, and with sulfides of copper, lead, bismuth, silver, and other metals. In uranium-iron ore deposits it occurs in association with hematite, magnetite, and other minerals. It also occurs in sedimentary deposits and in conglomerates, where powdery, earthy aggregates of the mineral are also commonly formed. Pitchblende is one of the most commercially important minerals contained in uranium ores.
G. P. BARSANOV