This. Rare earths aren't actually rare at all. They are everywhere. The thing is: unlike iron or copper, they don't naturally occur in high concentrations. A few percent here, a few percent there - it's refining them that is the problem.

This tends to involve lots of weird chemicals, and in the past mining operations were not particularly careful about what happened with those chemicals. Hence, the reason that the West left it to places that didn't care so much about pollution.

However, with modern technology, it is perfectly possible (if not necessary cheap) to refine without destroying the surrounding countryside. One just has to want to do it.