Australia has the world’s largest single uranium minerals deposit located 560 km north of Adelaide. The three main uranium minerals at this site are uraninite, coffinite and brannerite. Uranium is extracted from these minerals using a series of processes (grinding, acid dissolution, extraction). Of these uranium bearing minerals, brannerite is clearly the most resistant to acid dissolution. Brannerite is a titanate based mineral with a general formula of UTi2O6. Natural brannerites however commonly contain a number of other elements which replace the U and /or Ti atoms including Pb, Ca, Th, Y and rare earth elements (U substitutes) and Si, Al and Fe (Ti substitutes). The extent of crystallinity of natural brannerites can also vary due to a process referred to as metamictization which involves damage of the crystal structure from radiation emitted by the uranium atoms. Due to projected future increases in uranium demand there has been increased interest in extracting uranium from refractory uranium minerals such as brannerite.

In this study we have investigated the physical and chemical characteristics and dissolution of different forms of brannerite (un-substituted synthetic, natural and different substituted synthetic forms). The physical and chemical characteristics of the different brannerites were investigated using a combination of techniques including x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy-energy dispersive x-ray and diffuse reflectance infrared Fourier transform spectroscopy. The dissolution properties of the different brannerites were compared and are discussed based on there differing physical and chemical characteristics.