The second-to-last row of the periodic table contains 17 elements that play a central role in the manufacturing of smartphones, electric vehicles, medical devices, and other technologies. The so-called rare earth elements have special chemical make-ups that give them particular magnetic properties and other advantages. These traits come from the unique arrangement of the electrons in their atoms’ outer shell: some orbit close to the atomic nucleus and tend not to interact with the atoms’ outside environment, and so they rarely form bonds. The result is that they have predictable, dependable chemical properties.

How much has been extracted? Humans have mined about 4.5 million metric tons of rare earth elements so far. Most of those have come from China, which leads the world in the infrastructure and expertise to extract these minerals. The major U.S. source is the Mountain Pass deposit in southern California.