| uchucchacuaite | AgPb3MnSb5S12 |
| uhligite | Ca3(Ti,Al,Zr)9O20 |
| uklonskovite | NaMgSO4F·2H2O |
| ulexite | NaCaB5O6(OH)6·5H2O |
| ullmannite | NiSbS |
| ulrichite | CaCuUO2(PO4)2·4H2O |
| ulvospinel | TiFe2O4 |
| umangite | Cu3Se2 |
| umbite | K2ZrSi3O9·H2O |
| umbozerite | Na3Sr4ThSi8(O,OH)24 |
| umohoite | UO2MoO4·4H2O |
| ungarettiite | NaNa2Mn2Mn3Si8O24 |
| ungemachite | K3Na8Fe(SO4)6(NO3)2·6H2O |
| upalite | Al(UO2)3(PO4)2O(OH)·7H2O |
| uralborite | CaB2O2(OH)4 |
| uralite | actinolite |
| uralolite | Ca2Be4(PO4)3(OH)3·5H2O |
| uramphite | (NH4)2(UO2)2(PO4)2·6H2O |
| urancalcarite | Ca(UO2)2CO3(OH)6·3H2O |
| uraninite | UO2 |
| uranmicrolite | (U,Ca,Ce)2(Ta,Nb)2O6(OH,F) |
| uranocircite | Ba(UO2)2(PO4)2·12H2O |
| uranophane | Ca(UO2)2[SiO3(OH)]2·5H2O |
| uranophane-beta | Ca(UO2)2[SiO3(OH)]2·5H2O |
| uranopilite | (UO2)6SO4(OH)10·12H2O |
| uranopolycrase | (U,Y)(Ti,Nb)2O6 |
| uranosilite | USi7O17 |
| uranospathite | HAl(UO2)4(PO4)4·40H2O |
| uranosphaerite | Bi2U2O9·3H2O |
| uranospinite | Ca(UO2)2(AsO4)2·10H2O |
| uranotungstite | (Fe,Ba,Pb)(UO2)2WO4(OH)4·12H2O |
| uranpyrochlore | (U,Ca,Ce)2(Nb,Ta)2O6(OH,F) |
| urea | CO(NH2)2 |
| ureyite | kosmochlor |
| uricite | C5H4N4O3 |
| ursilite | (Mg,Ca)8(UO2)8(Si2O5)11(OH)10·26H2O |
| urvantsevite | Pd(Bi,Pb)2 |
| ushkovite | MgFe2(PO4)2(OH)2·8H2O |
| usovite | Ba2CaMgAl2F14 |
| ussingite | Na2AlSi3O8OH |
| ustarasite | Pb(Bi,Sb)6S10 |
| utahite | Cu5Zn3(TeO4)4(OH)8·7H2O |
| uvanite | U2V6O21·15H2O |
| uvarovite | Ca3Cr2(SiO4)3 |
| uvite | (Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4 |
| uytenbogaardtite | Ag3AuS2 |
| uzonite | As4S5 |