The only actinides found in appreciable quantities in the earth's crust are thorium and uranium, although small quantities of neptunium and plutonium have been found in uranium ores. As decay products of some thorium and uranium isotopes, actinium and protactinium are found in nature.

Are actinides found in nature?

Compared to the lanthanides, which (except for promethium) are found in nature in appreciable quantities, most actinides are rare. Most do not occur in nature, and of those that do, only thorium and uranium do so in more than trace quantities.

Which actinides are found naturally on Earth?

Five actinides have been found in nature: thorium, protoactinium, uranium, neptunium, and plutonium.