90Th Thorium

Year Discovered


Discovered By

Jons Jakob Berzelius of Sweden

Biological Rating

Not necessary for life.


Named after the Nordic god Thor, thorium is a silvery, radioactive metal. It is one of the least reactive of the actinides, reacting with water and acids but stable with air and bases. Thorium is the most common actinide and is believed to be about as common as lead in the Earth’s crust. More energy is available in the Earth’s thorium supply than in all of the uranium and fossil fuels combined. Thorium and uranium are mostly responsible for heating the Earth’s interior. Thorium and its compounds have very high melting points and are used in several high temperature applications, such as incandescent gas mantles, tungsten filament coatings and high temperature lab equipment. It is used in certain alloys, especially with magnesium. Thorium compounds have interesting optical qualities and are used in certain camera lens and other optical instruments. Lastly, thorium is used as nuclear energy fuel, but is not as efficient a fuel as uranium, and the technology to properly utilize it is not yet available. The most stable isotope of thorium has a half-life of 14,000,000,000 years.

Biological Benefits

Thorium has no biological use.

Role in Life Processes

No known benefit for life processes in plants and animals.


Thorium and uranium are the only naturally occurring actinides that are sufficiently common they can be mined. Thorium is obtained from the minerals monazite and thorianite (thorium dioxide). Thorium occurs as a significant impurity in the minerals zircon, titanite, gadolinite and betafite. It is mined in Australia, Canada, the USA, Russia and India.