WSJ story on how China is broaching notion of letting foreign companies enter into joint ventures on rare-earth mining/processing in Mongolia in exchange for access to technology--a well-established Chinese pattern that can backfire for foreign firms as time passes. This is described as a shift from "technology for market" to "technology for resources."
China does control--currently--about 95% of production, but only because it's cheap prices drove other mines out of competition.
But in reality, China accounts for only 30% of the world's known reserves, and existing mines can all be restarted within a couple of years. So China only "controls" because it keeps the price low.
China bans foreign companies from entering into the mining process itself, but allows cooperation on processing. China also imposes export quotas, which inevitably--as even the Chinese admit--will encourage competing production around the world.