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SR-11 (Ike #1 Mine) Designated Mining Operation <br /> January 31, 1995 - Page 6 <br /> Slick Rock district. It can also be seen that a significant <br /> increase in total COZ at slightly alkaline (pH 7 . 6 - 8.4) and <br /> slightly reducing (Eh-.2) conditions would make water capable of <br /> carrying uranium and vanadium together in solution. This amount of <br /> COZ (greater than 440 ppm) exists in natural ground water, as shown <br /> in some Salt Wash spring samples, but is unlikely in rain and near <br /> surface rain infiltrate as shown by analyses of shallow mine sump <br /> water. & a <br /> One of the reasons the vanadates are so insoluble is the crystal <br /> structure. These and the arsenates and phosphates form minerals <br /> with sheet structures, which can be "infinite" sheets as compared <br /> to the more soluble "finite" crystalline carbonate and sulfate <br /> minerals. "As soon as U+6 encounters V+5 in solution, there is a <br /> tendency to build up claylike sheets which are held together <br /> loosely by whatever cation happens to be in solution and by water <br /> molecules. " (Garrels & Christ, U.S.G.S. Prof. Paper 320, p. 88) . <br /> Potassium in solution is preferentially taken up in the interlayer <br /> of sheets even when Ca is more concentrated. This is the reason <br /> carnotite forms easier than tyuyamunite. Carnotite is one or two <br /> orders of magnitude more stable than tyuyamunite once it forms <br /> because the K+ forms stronger bonds of the sheets than Ca+2 because <br /> it is a larger ion. Tyuyamunite may be more abundant that <br /> carnotite in recently formed joint coatings from the high content <br /> of Ca in natural, near-surface ground waters as compared to the low <br /> K content. It is also more likely to form on ore fragments of a <br /> waste dump than carnotite. <br /> Oxidation must be complete to both U+6 and V+5 before carnotite or <br /> tyuyamunite can form (Garrels and Christ, U.S.G. S. Prof. Paper 320, <br /> p 88) . As previously mentioned, uranium usually reaches +6 before <br /> all the vanadium is oxidized to +5. Therefore, during weathering <br /> of ore, there is probably a stage in which U+6 would be readily <br /> leachable in very dilute acid if the vanadium could be prevented <br /> from oxidizing to the V+5state and the necessary amount of <br /> carbonate was also present. Such conditions could exist on a <br /> weathering mine dump. However, for it to become a pollution <br /> problem, it would require flushing to remove the uranium. In the <br /> semi arid Slick Rock District, the dump material will be wetted <br /> intermittently allowing for in-place moist oxidation to occur <br /> rather than leaching and flushing. <br /> No other toxic-forming materials besides uranium and vanadium exist <br /> in the rocks which will compose the waste dump. Even though these <br /> clastic sediments are permeable and subject to chemical weathering, <br /> it must be remembered that the rock-forming constituents of fluvial <br /> sediments are already at equilibrium with the surficial <br /> environment. However, ore minerals are not, but have been <br /> discussed above. Shawe (1968) has shown that "the ore-bearing <br /> sandstone of the Salt Wash Member of the Morrison Formation is not <br /> unique in mineral composition, and its mineral composition probably <br />