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Precipitation/Dissolution <br />Precipitation and dissolution of uranium minerals in pure phases and solid-solution <br />phases are discussed below. <br />Pure Phases <br />Uranium minerals can be divided into U(IV) minerals, the most important of which is <br />uraninite (U02) and U(VI) minerals, which tend to be more soluble. U(VI) minerals <br />include phosphates such as autunite, oxides like gummite, and nitrates which are very <br />soluble. Some of the possible uranium minerals are shown in Table 3. <br />Table 3 <br />Pnacil?la i iraninm MinPralc <br /> <br />Mineral Name Formula <br />- U02 3 P04 2 <br />Autunite Ca UOz z PO4 2 <br />- U02(OH)2 <br />Bassetite Fe U02 2 P04 2 <br />Gummite U03 <br />H-Autunite H2 U02 2 P04 2 <br />K-Autunite K2 U02 z PO4 z <br />Na-Autunite Naz U02 z P04 z <br />Nin oite CaU P04 2:2H2O <br />Rutherfordine U02CO3 <br />Saleeite M UO2 2 P04 2 <br />Schoe ite U02(OH)2:H20 <br />- U HP04 2 <br />- U308 <br />- U409 <br />Amorphous Uraninite U02 <br />- UOz NO3 2 <br />- UOz N03 2:2H2O <br />- UOz NO3 2:3H2O <br />- U02(N03)2:6H20 <br />- U03 <br />Uraninit:e U02 <br />• <br /> <br />U(VI) silicates can be important where dissolved silica concentrations are significant. <br />Important silica minerals include uranophane [Ca(UO)2Si202:6H20] and similar phases. • <br />As silica was not analyzed at the site, these phases were not included in Table 5-3. In