Xenotime

Xenotime
Xenotime with rutile
General
CategoryPhosphate minerals
Formula
(repeating unit)
YPO4
IMA symbolXtm[1]
Strunz classification8.AD.35
Crystal systemTetragonal
Crystal classDipyramidal (4/mmm)
H-M symbol: (4/m)
Space groupI41/a
Identification
ColorBrown, brownish yellow, gray
Crystal habitPrismatic, radial aggregates, granular
CleavagePerfect [100]
FractureUneven to splintery
Mohs scale hardness4.5
LusterVitreous to resinous
StreakPale brown, yellowish or reddish, to white
DiaphaneityTranslucent to opaque
Specific gravity4.4–5.1
Refractive index1.720–1.815
Birefringenceδ = 0.096
PleochroismDichroic
Other characteristicsNot radioactive or luminescent
References[2][3][4][5]

Xenotime is a rare-earth phosphate mineral, the major component of which is yttrium orthophosphate (YPO4). It forms a solid solution series with chernovite-(Y) (YAsO4) and therefore may contain trace impurities of arsenic, as well as silicon dioxide and calcium. The rare-earth elements dysprosium, erbium, terbium and ytterbium, as well as metal elements such as thorium and uranium (all replacing yttrium) are the expressive secondary components of xenotime. Due to uranium and thorium impurities, some xenotime specimens may be weakly to strongly radioactive. Lithiophyllite, monazite and purpurite are sometimes grouped with xenotime in the informal "anhydrous phosphates" group. Xenotime is used chiefly as a source of yttrium and heavy lanthanide metals (dysprosium, ytterbium, erbium and gadolinium). Occasionally, gemstones are also cut from the finest xenotime crystals.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Fontani, Marco; Costa, Mariagrazia; Orna, Virginia (2014). The Lost Elements: The Periodic Table's Shadow Side. Oxford University Press. p. 73. ISBN 978-0199383-344.
  3. ^ "Mindat database".
  4. ^ "Xenotime". Webmineral.
  5. ^ "Handbook of Mineralogy" (PDF).