| > All that has to happen is a stable solid. What does that mean? Rare earths are "rare" for two reasons - they are spread about and don't appear in high concentrartions - at least one is "as common" in the crust as copper but it doesn't form in massive lumps of "quite a lot together" in the manner of copper (which forms in several types of clumps, eg [1]). The other reason they are rare is that they are mostly geochemically bound to other things in the way that silver and gold are not - a strong chemically reaction is required to free them and make them appear - that's a lot of wetwork with acids | reactive gases | etc [2]. [1] https://en.wikipedia.org/wiki/Porphyry_copper_deposit [2] https://www.britannica.com/science/rare-earth-element/Proces... Additionally (each ~ an hour) The Chemistry and Geology of the Clay Rare Earths: https://www.youtube.com/watch?v=GFwrg4wWsm4 Options for the separation of Rare Earth Elements: https://www.youtube.com/watch?v=fMbsOjj_hls (or search and find a lecture | paper of your preference) |