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Uranospathite: Al1-x[ ]x[(UO2)(PO4)]2(H2O)20+3xF1-3x
Comments: Minute, less than 0.1cm platy yellow crystals or uranospahtite on matrix. Location: Pedro Alvaro, Salamanca, Spain. Scale: Picture size 1 cm. © Tom Loomis / Dakota Matrix
Uranosphaerite: Bi(UO2)O2(OH)
Comments: Yellow-orange earthy uranosphaerite crusts. Location: Kersegalec en Lignol, Vendee, France. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Uranospinite: Ca(UO2)2(AsO4)2·10(H2O) Metauranospinite: Ca(UO2)2(AsO4)2·8(H2O)
Comments: Translucent platy uranospinite (probably dehydrated to metauranospinite) microcrystals on matrix. Location: Grube Buhlskopf, near Ellweiler, Rheinland-Pfalz, Germany. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Uranpyrochlore: (U,Ca,Ce)2(Nb,Ta)2O6(OH,F) Samarskite-(Y): (Y,Fe+++,U)(Nb,Ta)5O4
Comments: Deep greenish-brown resinous crystalline massive uranpyrochlore with black samarskite-(Y). Location: Beryl Hill, near Yinnietharra Station, Western Australia, Australia. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Urea: CO(NH2)2
Comments: SEM image of tetragonal prismatic crystals of urea. Location: Ghar al Hibashi Harrat Nawasif/Al Buqum, Kingdom of Saudi Arabia. Scale: See Image. © Saudi Geological Survey
Uricite: C5H4N4O3
Comments: White powdery uricite aggregate. Location: Dingo Donga Cave, near Rawlinna, Western Australia, Australia. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Urusovite: Cu[AlAsO5]
Comments: Green urusovite grain. Location: Northern Breakthrough, Great Fissure (Main Fracture) eruption, Tolbachik volcano, Kamchatka Oblast', Far-Eastern Region, Russia. Scale: Crystal length 0.7 mm. © Thomas Witzke / Abraxas-Verlag
Urvantsevite: Pd(Bi,Pb)2
Comments: Epoxy grain mount of a fragment of urvantsevite (Urv). Location: Talnakh Cu-Ni deposit, near noril'sk, Krasnoyarsk region, Russia. Scale: See Image. © Diederik Visser
Ushkovite: MgFe+++2(PO4)2(OH)2·8(H2O) Roscherite: Ca(Mn++,Fe++)5Be4(PO4)6(OH)4·6(H2O)
Comments: Translucent ushkovite microcrystals with orange roscherite on feldspar. Location: Galileia, Minas Gerais, Brazil. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Usovite: Ba2CaMgAl2F14
Comments: B&W BSE image of a fragment of usovite (Us) and fluorite (Fl) in an epoxy grain mount section. Location: Pravaya Noiba River (tributary if the Teya), northeastern Enisei Range, Krasnoyarsk region, Russia. Scale: See Image. © Diederik Visser
Ussingite: Na2AlSi3O8(OH) Cuprostibite: Cu2(Sb,Tl)
Comments: Massive ussingite hosting grains of the very rare copper antimony-thallium bearing cuprostibite. Location: Ilimaussaq, Tasseq, Greenland. Scale: 4.8 x3.4 cm. © John Veevaert
Ussingite: Na2AlSi3O8(OH) Vuonnemite: Na11Nb2TiSi4O12(PO4)2O5F2
Comments: Massive, violet colored ussingite with a single bladed partial crystal of white vuonnemite 1.5 cm in length. Location: Mt. Karnasurf, Lovozero, Russia. Scale: 4.2 x 3 cm. © John Veevaert
Ussingite: Na2AlSi3O8(OH) Gerasimovskite: (Mn,Ca)(Nb,Ti)5O12·9(H2O) (?)
Comments: Pale tan gerasimovskite pseudomorphous after epistolite crystal, in purple ussingite. Location: Lovozero Massif, Kola Peninsula, Murmansk District, Russia. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Utahite: Cu5Zn3(Te++++++O4)4(OH)8·7(H2O)
Comments: Blue utahite grain in matrix. Location: Centennial Eureka Mine, Tintic District (East Tintic Mountains), Juab Co., Utah, USA. Scale: Picture size 1 mm. © Thomas Witzke / Abraxas-Verlag
Uvanite: U++++++2V+++++6O21·15(H2O)
Comments: Yellowish brown uvanite coating on sandstone. Location: Temple Rock, Emery County, Utah, USA. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species
Uvarovite: Ca3Cr2(SiO4)3
Comments: Green uvarovite (garnet) crystal group. Location: Mokkivaara mine, Outokumpu, Finland. Scale: 1.3x1.2x1 cm. © Fabre Minerals
Uvite: (Ca,Na)(Mg,Fe++)3Al5Mg(BO3)3Si6O18(OH,F)4
Comments: Reddish brown, prismatic uvite crystals. Location: Brumado, Bahia, Brazil. Scale: 4.5 x 5.5 cm. © Fabre Minerals
Uytenbogaardtite: Ag3AuS2
Comments: Gray crystal grains of uytenbogaardtite to 1mm throughout matrix with electrum. Location: Bullfrog mine, Nye County, Nevada, USA. Scale: Slab 1cm thick 6x6cm. © Tom Loomis / Dakota Matrix
Uzonite: As4S5
Comments: Yellow powdery uzonite encrustation. Location: Uzon Volcano, Kamchatka District, Russian Far East, Russia. Scale: See Photo. © Jeff Weissman / Photographic Guide to Mineral Species