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a mineral; yttrium phosphate, YPO4 (V2O3 ~ 63.1 percent). Xenotime always contains rare earths, sometimes ThO2, UO2 (up to 5 percent), ZrO2 (up to 3 percent), and others. It crystallizes in the tetragonal system, forming pyramidal or prismatic crystals; it is isostructural with zircon. Xenotime is light brown or reddish brown in color. It has a hardness of 4–5 on the mineralogical scale and a density of 4,450-4,590 kg/ m3. It occurs in granites and pegmatites in the form of granules or crystals ingrown into feldspar or quartz; it also occurs in alluvial deposits. Xenotime is closely associated with monazite and zircon.
The best-known deposits of xenotime are the pegmatite and alluvial deposits of Brazil (Minas Geraes) and the pegmatites of Norway (Hitterö, near Arendal, and Kragerö in Telemark) and Sweden (Ytterby). In the USSR, xenotime is found in the pegmatites of Karelia.