Rare earth elements provide much of the boost to high tech gadgets. Their particular properties are useful in producing colors in electronic video screens, and enhanced magnetic properties in high performance magnets. Traditionally the mining was mostly from one mine in California. As the "rarer" rare earths started being produced in quantity, new uses were found for them. So China stepped in and gradually monopolized the industry. We've found so many uses for the "rarer" rare earths, that modern society would have difficulty functioning without them.
The "rare" in rare earths is misleading. Most of the rare earths are rare only in the sense that they are so dispersed within the earth, that it is difficult to find economically mineable deposits of them.
Some geology. Forget about the global warming/climate change scamsters. They haven't a clue. Rare earths become mineable through real changes in climate, and humans have nothing to do with it.
The earth is currently in an ice age, and has been for the past few million years. These run in cold/hot cycles, with current cycles running about 100,000 years. Most of the time, perhaps 80% of it, the world has been bitterly cold. Currently we are in a warm part of the cycle which, if geological history is a guide, is probably much closer to the end of the warm period, than the beginning. And there probably isn't much we can do about it.
The CO2 story is backwards. The scamsters jumped at some new scientific data, which eventually turned out to show that a warming earth increases the CO2, not the other way around. The CO2 gets mildly boiled out of the oceans with increases in temperature. They couldn't admit they were wrong, so they developed climate models that figuratively show that the cart really can push the horse.
The earth's temperature fluctuates in cycles, much as the ocean tide goes out, and comes back in again. The earth has been warming for the last 11,700 years, with the end of the Younger Dryas geological period. Continuously melting ice sheets and glaciers have affected the climate over time.
The spin of the earth is perhaps the major player in this. The earth has east/west bands of moisture (rain) which, over the span of thousands of years, repeatedly migrate north and south. Ancient Roman traders knew of a northern Sahara Desert which was much wetter than it is now. Changes in the amount of moisture has caused water tables (the depth you have to drill in the earth to reach underground water) to rise and fall, in conjunction with the amount of rainfall. This change in water tables, in areas of thick sediment, dissolves rare earths out of the soil, and re-deposits them again. This concentrates the rare earths (bauxite, too, the main ore of aluminum).
There's a relatively easy way to mine rare earth elements that have been concentrated this way. You go to the top of a hill, drill a long vertical hole in it, and insert a perforated pipe in it. Then you insert horizontal pipes at the bottom of the hill. Poor an industrial solvent into the top of the hill, and collect the liquid which flows out the bottom of the hill. This will be heavily enriched with rare earth elements.
While this is relatively cheap to do, it destroys the ground around it, probably for a few generations. The pH of the soil gets zapped, and there are all sorts of metals added to the soil in such quantities that they are no longer trace amounts, they are in high enough concentrations as to be poisonous.
When China first mined rare earths, it largely used this solvent method. The Chinese grew tired of seeing their land ruined, and shut down these miners. So instead China imported this rare earth ore from North Korea (not enough farm land already) and Myanmar. Where in Myanmar? The Kachin State. My understanding is that the military government buys peace from the locals by allowing them to mine rare earth elements this way.
But mining this way extracts only a tiny portion of the available rare earth elements, and wrecks the land. What if China and Myanmar coordinated to develop a sane and ecologically sustainable method of mining this? The Kachins can get a piece of the profits to keep them happy.