Uranium is found to some extent in the majority of rocks and sediments making up the Earth's crust, but is never found in concentrated deposits.
The most common uranium ore is pitchblende, which consists of a mixture of UO2 with U3O8. The largest known source of pitchblende is located in the Leopolville mines, in Congo, Africa.
Other uranium containing minerals are euxenite, carnotite, brannerite and coffinite. The largest deposits of these ores are located in the USA, Canada, Russia and France.