Thorium
A mildly radioactive by-product of rare-earth monazite, little used today but long promoted as a future nuclear fuel.
Tech & minor metals · No. 54
- Not on a critical list
India banned monazite sand exports in 1946 to keep its thorium, the radioactive metal long promoted as a future nuclear fuel.
Chart: Illustration: Thorium
Where it comes from
Chart: Map of where it comes from
Most thorium sits in monazite from heavy-mineral beach and river sands. Monazite is separated from ilmenite, rutile and zircon, then cracked for rare earths; only a little of its thorium is used.
Three things to know
- Thorium oxide has one of the highest melting points of any oxide, which once made it useful in lamp mantles and welding electrodes.
- Thorium-232 is fertile: in a reactor it converts to fissile uranium-233, which is why it is promoted as a nuclear fuel.
- The United States imported thorium compounds worth only about $118,000 in 2025, based on data through July.
The journey
- 1 Mineral sandsHeavy-mineral beach and river sands
- 2 MonaziteRare-earth and thorium phosphate concentrate
- 3 CrackingChemically split to recover rare earths
- 4 Thorium residueMostly stored, a little refined
- 5 ProductsOxide, nitrate and alloys