Well-known minerals containing yttrium include gadolinite, xenotime, samarskite, euxenite, fergusonite, yttrotantalite, yttrotungstite, yttrofluorite (a variety of fluorite), thalenite, yttrialite.
en.wikipedia.org The refractive index of xenotime is 1.720-1.815 with a birefringence of 0.095 (uniaxial positive).
en.wikipedia.org Many minerals contain europium, with the most important sources being bastnsite, monazite, xenotime and loparite.
en.wikipedia.org Due to uranium and thorium impurities, some xenotime specimens may be weakly to strongly radioactive.
en.wikipedia.org Xenotime is used chiefly as a source of yttrium and heavy lanthanide metals (dysprosium, ytterbium, erbium, and gadolinium).
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