Radioactive waste also plays a significant role. Uranium tailings are waste by-product materials left over from the rough processing of uranium-bearing ore. They are not significantly radioactive. Mill tailings are sometimes referred to as 11(e)2 wastes, from the section of the Atomic Energy Act of 1946 that defines them. Uranium mill tailings typically also contain chemically hazardous heavy metal such as lead and arsenic. Vast mounds of uranium mill tailings are left at many old mining sites, especially in Colorado, New Mexico, and Utah. Although mill tailings are not very radioactive, they have long half-lives. Mill tailings often contain radium, thorium and
Uranium ore uranium content) in the Czech Republic. Also they are closely related to the granites, the mineralization is much younger with a time gap between granite formation and mineralisation of 20 million years. The initial uranium mineralisation consists of quartz, carbonate, fluorite and pitchblende. Remobilsation of uranium occurred at later stages producing polymetal veins containing silver, cobalt, nickel, arsenic and other elements. Large deposits of this type can contain more than 1,000 individual mineralized veins. However, only 5 to 12% of the vein areas carry mineralization and although massive lenses of pitchblende can occur, the overall ore grade is only about