In its pure form, uranium is a silvery white metal of very high density, more dense even than lead. Uranium can take many chemical forms, but in nature it is generally found as an oxide
(in combination with oxygen).

Triuranium octoxide (U3O8) is the most stable form of uranium oxide and is the form most commonly found in nature.

Uranium is one of the most abundant elements found in the Earth's crust. It can be found almost everywhere in soil and rock, in rivers and oceans. Traces of uranium are even found in food and human tissue. However, concentrated uranium ores are found in just a few places, usually in hard rock or sandstone.

The concentrations of uranium vary according to the substances it is mixed with and according to the places where it is found. For example, when uranium is mixed with granite that covers 60% of the Earth's crust, there are approximately four parts of uranium per million, i.e. 999,996 parts of granite and four parts of uranium.

Concentrations of uranium that are economic to mine are considered ore. Uranium is present in low concentrations in many rocks and bodies of water, but extraction is only economically viable from richer deposits. The decision to mine is a function of many factors including extraction method, market prices and social and environmental considerations.
Uranium deposits are found all over the world. The largest deposits of uranium are found in Australia, Kazakhstan and Canada. High-grade deposits are only found in Canada.