Uranium is a radioactive element that occurs naturally in low concentrations (a few parts per million) in soil, rock, and surface and groundwater. It was discovered in 1789 by German chemist Martin Klaproth in the Joachimsal silver mines of the present day Czech Republic. In 1896 Polish-French physicist and chemist Maria Sklodowska-Curie discovered the radioactive properties of uranium.

Uranium in its pure form is a silver-colored heavy metal that is nearly twice as dense as lead. It is the heaviest naturally occurring element, with an atomic number of 92. In nature, uranium atoms exist as several isotopes: primarily uranium-238, uranium-235, and a very small amount of uranium-234. (Isotopes are different forms of an element that have the same number of protons in the nucleus, but a different number of neutrons.) In a typical sample of natural uranium, most of the mass (99.27%) consists of atoms of uranium-238. About 0.72% of the mass consists of atoms of uranium-235, and a very small amount (0.0055% by mass) is uranium-234.

Since uranium occurs in trace amounts (0.2-5.0ppm) in virtually all rocks, exploration for uranium is essentially the search for geological environments in which economic concentrations of uranium may have been produced. Uranium can take many chemical forms, but in nature it is generally found as an oxide. Triuranium oxtoxide (U308) is the most stable form of uranium oxide and is the form most commonly found in nature. Uranium exploration uses most techniques employed in the search for oil, gas and all other minerals, as well as some unique to uranium. Initial target areas are large, and, as smaller areas of potential are recognizsed, more intense methods are used. Geology, remote sensing, geophysics, geochemistry, geobotany and exploration drilling are all used at the same time.

Geological mapping and basin analysis helps in the choice of geological environments which are potentially favourable for uranium occurrences. Remote sensing using satellite imagery and aerial photography is used as part of this initial stage. Follow-up surveys using airborne or ground gamma-ray spectrometry to detect high-energy gamma radiation from the decay of radioactive minerals associated with uranium are used in the later stages of the exploration. Geochemical surveys of stream and lake sediments are commonly used to detect broad chemical anomalies and provide information on sub-surface environments. Stream and lake sediment surveys enable the systematic sampling of the uranium content of bedrock terrain over large areas and in any kind of vegetative and soil cover. Once a promising target is found, detailed exploration techniques are applied to carefully locate deposits, determine their size, shape and depth, and the concentration of uranium and other useful minerals. The techniques include the collection of geochemical and geophysical data from closely spaced locations as well as from drilling and the analysis of large samples. The final step is to see if it is possible to extract and separate the useful materials.

Uranium is found all over the world. The largest known deposits of uranium are found in Australia, Kazakhstan and Canada.

Source: Uranium 2005: Resources Production and Demand. OECD/IAEA. Based on identified resources which consists of reasonably assured resources and inferred resources at a cost of less than $80(US) per kilogram of uranium as at January 1, 2005.

Uranium is removed from the ground in of three methods depending on the characteristics of the deposit. The three methods are open pit mining, underground mining and in situ leach.

The open pit mining method is used to extract uranium when uranium ore is found near the surface, generally less than 100 metres deep. Soil and waste rock are removed to expose the hard rock. Then a pit is excavated to access the ore. The walls of the pit are mined in series of benches to prevent collapsing. The rock is broken by using explosives. The broken rock is hauled to the surface in large trucks for milling.

The underground mining method is usually used when uranium ore is located more than 100 metres below the surface. The ore is accessed by digging vertical shafts to the depth of the orebody. Then a number of tunnels are dug around the uranium deposit. In addition a number of horizontal tunnels are dug. These horizontal tunnels provide access to the mine and ventilation. The ore is blasted and hoisted to the surface for milling.