|
| |
One of six radioactive elements that occur naturally: potassium, rubidium,
thorium, uranium, and associated radium, samarium, and lutecium. Thorium
commonly occurs in monazite, a sparsely scattered accessory mineral of
certain granites, gneisses, and pegmatites. It is concentrated, however,
by weathering processes in sands and gravels as commercial placer deposits
along rivers and beaches. The most important primary uranium ore minerals
are davidite and uraninite, esp. pitchblende, the massive variety. These
minerals are of rather underspread occurrence in certain granites and
pegmatites and occur as secondary minerals in metallic vein deposits. The
secondary uranium minerals, however, are more underspread and more
numerous than the primary uranium ore minerals. Secondary uranium minerals
are found in weathered and oxidized zones of primary deposits and, also,
in irregular flat-lying sandstones, such as those in the Colorado Plateau,
where the uranium mineralization was precipitated from solutions.
Carnotite, the potassium uranium vanadate of conspicuous yellow color, is
perhaps the most important of the secondary uranium ore minerals. Others
are tyuyamunite, which is closely related to carnotite, and the
torbernites and autunites which are uranium minerals.
Source:
Dictionary of Mining, Mineral, and Related Terms
| |
|
