The Arizona Geological Survey has just published a report on rare earth element potential in New Mexico by Virginia T. McLemore. The full report is available for free download here (6Mb). The report was produced as part of the 48th Annual Forum on the Geology of Industrial Minerals.
From the report:
“The REE (rare earth element) family includes 15 lanthanide elements (atomic number 57-71), yttrium (Y, atomic number 39), and scandium and are commonly divided into two chemical groups, the light REE (La through Eu) and the heavy REE (Gd through Lu, Sc, and Y). REE are lithophile elements (or elements enriched in the crust) that have similar physical and chemical properties, and, therefore, occur together in nature. However, REE are not always concentrated in easily mined economic deposits and only a few deposits in the world account for current production.”
There are several types of rare earth element deposits. The report discusses deposits in alkaline igneous rocks, carbonatites, REE-Th-U hydrothermal veins, pegmatites, placer deposits, and other REE-bearing deposits.
The report contains several interesting photographs and illustrative diagrams, and an appendix listing the mining districts and type of deposits contained therein. Give it a look.