Rare earth metals were discovered in the early 1800's.
Contrary to the name, these metals are relatively plentiful. The difficulty in extracting them is that they are widely dispersed and seldom found in economic quantities. .India, Brazil, the U.Ssouth Africa and most recently China are major producers of rare earth metals.
These metals are in high demand for high tech. (lasers, camera lenses, and computers), energy (batteries and super-conductors)) and industry (aerospace).