Uranium ore deposits are concentrations of uranium in the Earth's crust, which can be mined for profit. Uranium is very common, being 40 times more common than silver.[1] Uranium ore refers to naturally occurring rock or mineral deposits that contain a sufficient concentration of uranium to make its extraction economically viable.[2][3] Uranium is a relatively rare element and is typically found in trace amounts in the Earth’s crust. Uranium ore can be mined from open pits or underground excavations and can then be crushed and treated at a mill to separate the valuable uranium from the ore. Uraninite is a major ore mineral of uranium and is the chief source of uranium.[4]