Uranium is present in most earth and water, but it is most commonly extracted from high-concentration sources such as pitchblende, uraninite, carnotite, autunite, phosphate rock, lignite or monazite sand. Uranium was first obtained in 1789 from pitchblende, which mostly contains uranium oxides. As a metal, it was later extracted in 1841 by heating uranium dioxide and potassium.
The radioactivity of this element was not discovered for almost another 60 years.
The small amounts of uranium that occur naturally in the environment are in continuous flux with the weather to form concentrations that can be mined by humans. It is then refined for use in manufacture and inevitably returned to the environment as pollution.