| Noun | 1. | xenotime - a brown-to-yellow mineral that is a phosphate of yttrium in crystalline formatomic number 69, thulium, Tm - a soft silvery metallic element of the rare earth group; isotope 170 emits X-rays and is used in small portable X-ray machines; it occurs in monazite and apatite and xenotime atomic number 70, Yb, ytterbium - a soft silvery metallic element; a rare earth of the lanthanide series; it occurs in gadolinite and monazite and xenotime atomic number 39, Y, yttrium - a silvery metallic element that is common in rare-earth minerals; used in magnesium and aluminum alloys mineral - solid homogeneous inorganic substances occurring in nature having a definite chemical composition | |