Conventional rare earth element mineral deposits: The global landscape
Four conventional mineral deposit types—carbonatite, alkaline igneous, heavy mineral sand, and regolith-hosted ion-adsorption clay deposits—currently supply global markets with the rare earth elements (REEs) and rare earth oxides (REOs) necessary to meet the technological needs of global communities. The unique properties of REEs make them useful in a wide variety of applications, such as alloys, batteries, catalysts, magnets, phosphors, and polishing compounds. Rare earth element minerals are complex in both composition and structure. Carbonate, oxide, silicate, and phosphate-type minerals contain highly variable amounts of rare earths. Most rare earth-bearing minerals contain mainly lighter rare earths, a mixture of all the rare earths, or only the heavier rare earths. Diverse technological applications require the full range of light, middle, and heavy rare earths. The production of these elements, in particular the heavy rare earths, remains highly dependent on deposits from China. Diversification of rare earth supply chains is contingent on expanded knowledge of globally distributed resources and an understanding of the degree to which those resources have been explored and evaluated. The knowledge of tectonic setting, typical rock associations, deposit morphology, and deposit genesis has led to the discovery of many conventional-type rare earth deposit types. Recent developments are anticipated to result in further discoveries that have the potential to meet the ever-expanding applications of REEs and REOs to address modern societal needs.