Xenotime n. : A native phosphate of yttrium occurring in yellowish-brown tetragonal crystals.

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Taxonomy
xenotime, yttrium, minerals, lanthanides, zircon, free encyclopedia, brownish yellow, prismatic, aggregates, dipyramidal, vitreous, resinous, dysprosium, thorium, uranium, Occurrence, crystals, greenish brown.

Defination from the web:
Xenotime is a rare earth phosphate mineral, whose major component is yttrium orthophosphate (Y P O 4) ... Due to uranium and thorium impurities, some xenotime specimens may be weakly to strongly radioactive. ... Occasionally, gemstones are also cut from the finer xenotime crystals. ...