“Gel-zircon”, an unusual Zr-silicate phase from the Manibay uranium mine,northern Kazakhstan, was studied using X-ray diffraction (XRD), electronmicroprobe energy dispersive X-ray spectroscopy (EDS) and high resolutiontransmission electron microscopy (HRTEM). XRD results indicate thatgel-zircon is mostly amorphous and occurs with numerous impurity phases.Microprobe EDS results indicate a UO2 content up to 9.14 wt. %.HRTEM images revealed that the microtexture of gel-zircon consists ofnanocry stal lites of zircon, 2–10 nm in size, in a dominantly amorphousmatrix. Despite the U-Pb age of 420±25 my and the lack of significantcrystallinity, the gel-zircon is an apparently chemically durable phase.Leaching of uranium ores which contain gel-zircon as the major U-bearingphase is impossible using existing uranium plant technologies. Thealpha-decay dose, 2.64 displacements per atom (dpa), corresponding to theage of gel-zircon is much higher than that (0.5 dpa) required to causemetamictization of crystalline zircon. However, the morphology of gel-zirconwhich occurs as veins up to 5 mm thick and tens of mm long does not indicateinitial crystallinity. Initially crystalline natural zircons often preservetheir crystal morphology after metamictization. This amorphous phase isanalogous to the highly damaged state characteristic of zircon proposed as awaste form for the disposition of excess weapons plutonium.