Rare earths: why a smallmarket matters.

The rare earths are a group of seventeen elements. Despite the name, several of them are not especially rare in the Earth's crust; what is rare is finding them in deposits that can be mined and processed economically.

Their best-known use is in permanent magnets. Neodymium and praseodymium, often traded together as NdPr, form magnets that are much stronger than conventional ones, and small additions of dysprosium or terbium help them work at high temperatures. These magnets go into electric-vehicle motors, wind turbines, electronics and defence systems.

Mining produces a concentrate, often from minerals such as bastnäsite or monazite. The hardest step comes next: separating the individual elements, which behave very similarly chemically, takes many stages of solvent extraction. Separation capacity is concentrated in a small number of plants worldwide.

Concentrates are specified by their total rare-earth oxide content and by the distribution of individual elements, since the magnet elements carry most of the value. Thorium and uranium content is also checked, because it determines how the material can be transported and processed.

Because the market is small and processing is concentrated, rare earths appear on most lists of critical raw materials, and buyers look for documented, reliable supply chains.