WNA reported in 2024 that uranium occurs in a number of different geological environments. Most Kazakhstan uranium resources are sedimentary.
Most Canadian resources are unconformity-related. Most Australian uranium resources are in unconformity-related and iron oxide breccia complex orebodies.Most uranium deposits in the U.S. are in young sedimentary desposuotes called roll-fron deposits, while older deposits have been re-distributed in sandstones. Virginia is an exception occurring in metamphic rocks.
Uranium deposits worldwide are grouped into 15 major types based on their geological setting. Some categories have several sub-types. The most recent geological classification has been defined by the International Atomic Energy Agency (IAEA) in 2013 and has been adopted in the Red Book since 2014. The deposit types have fundamental characteristics and recognition criteria, and in that respect, while mainly named by host rock, the types are essentially empirical models, based on observable characteristics.
For a summary of all the known types of occurrences, see article.
Perspective
A comprehensive listing of world uranium deposits from a purely geological perspective includes much low-grade mineralisation which is subeconomic. There is very little recovery of uranium from the three deposit types with the largest estimated totals – lignite, black shale and phosphate. Three of the next most-abundant comprise most of the 6.1 million tonnes of identified recoverable resources listed in the 2018 Red Book, and contribute much of the world’s supply of uranium today: sandstone, iron-oxide breccia, and Proterozoic unconformity.
Uranium Minerals
The major primary ore mineral is uraninite (basically UO2) or pitchblende (U2O5.UO3, better known as U3O8), though a range of other uranium minerals are found in particular deposits. These include carnotite (uranium potassium vanadate), the davidite-brannerite-absite type uranium titanates, and the euxenite-fergusonite-samarskite group (niobates of uranium and rare earths).
Brannerite (uranium calcium titanium iron oxide, basically uranium titanate – UTi2O6 – with some calcium and other elements replacing uranium and some iron, and other elements replacing titanium) is particularly important since it occurs as up to 30% of the mineralisation at Olympic Dam and also (<10%) at Valhalla near Mount Isa. It does not dissolve readily in sulfuric acid, and so a substantial proportion is not recovered. Research is being undertaken to improve the recovery of this, which has significant implications for the quantum of Australian recoverable low-cost resources of uranium
A large variety of secondary uranium minerals is known, many are brilliantly coloured and fluorescent. The commonest are gummite (a general term like limonite for mixtures of various secondary hydrated uranium oxides with impurities); hydrated uranium phosphates of the phosphuranylite type, including autunite and ningyoite (with calcium), saleeite (magnesian) and torbernite (with copper); and hydrated uranium silicates such as coffinite, uranophane (with calcium) and sklodowskite (magnesian).
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