XenotimeREE

XenotimeREE is a term used in mineralogy to refer to xenotime minerals that contain notable concentrations of rare earth elements (REEs). Xenotime itself is a phosphate mineral with a general composition expressed as (REE, Y)PO4, where the REE component includes yttrium and heavier lanthanides. In practice, xenotimeREE denotes varieties in which one REE is dominant, leading to end-member names such as xenotime-(Y), xenotime-(Dy), xenotime-(Er), xenotime-(Yb), and xenotime-(Tm).

Chemically, xenotimeREE minerals crystallize in the tetragonal system and typically appear as brown to yellow-brown crystals or grains. The structure accommodates substitution of different REEs for yttrium, which influences properties such as color, density, and reflectance. Typical physical properties include a hardness around 5.5 and a specific gravity in the mid-4s. The minerals commonly occur as accessory constituents within granitic rocks, pegmatites, and hydrothermal veins, and they are frequently found in association with monazite, zircon, apatite, and fluorite.

Occurrence and exploration emphasize xenotimeREE as a potential source of heavy REEs, which are critical for modern technologies such as permanent magnets, catalysts, and phosphors. Economic extraction generally involves open-pit mining followed by processing steps like gravity concentration, flotation, and magnetic separation to concentrate the REE-bearing phases, with solvent extraction used to separate individual REEs. In addition to ore use, xenotime minerals can host uranium and thorium, making them relevant for geochronology and petrogenetic studies through U-Pb dating in certain geological settings.

In mineral nomenclature, xenotimeREE can be labeled as xenotime-(REE) to reflect the dominant rare earth in the crystal structure, highlighting both its mineral identity and its REE enrichment.