Where is uranium found in nature?
Uranium is not a rare element in nature. It averages about 2-4 ppm in the earth’s crust, which means it is more abundant than silver, tin, and zinc. In general, uranium tends to concentrate in felsic igneous rocks, and is noticeably depleted in most mafic rocks. Uranium is soluble and is easily transported by ground waters, and therefore uranium concentrations in bogs and reduced alluvium are not unusual. Owing in part to the two common valences of uranium (IV and VI) there are dozens of uranium minerals including uraninite, uranothorite, carnotite, autunite, thucolite, coffinite, and uranophane. Uranium does not occur in nature as a native element. The world’s biggest producer of uranium is Canada, with mines in Saskatchewan, which produce about 1/3 of the world’s uranium. Other uranium producing countries are Australia, Niger, Namibia, Kazakhstan, Argentina, and the US. Most uranium ore averages about 0.1 to 0.5%, but in Saskatchewan the ore is unusually high grade, in the range of 1
