What is Xenotime-(Yb)?
Xenotime-(Yb) is the ytterbium-dominant xenotime-group phosphate, a rare-earth mineral of unusual chemistry and specialist collector interest.
Mineralogy and structure
Reference formula: YbPO4. Xenotime-(Yb) is tetragonal and isostructural with xenotime-(Y). A xenotime-(Y) COD model is used as a labelled representative because no separate Yb-dominant public CIF was selected. Xenotime-(Yb) is classified with phosphates and has tetragonal crystal symmetry. Typical hardness is 4–5 on the Mohs scale and specific gravity is approximately 4.8–5.2.
Colour, lustre and habit
Typical colours include yellow, yellow-brown, brown, greenish brown. The usual prismatic, granular, massive habit and vitreous, resinous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Xenotime-(Yb) forms in or is associated with rare-earth pegmatites, alkaline complexes, metamorphic rocks and heavy-mineral concentrates. Important documented localities include Scandinavia, Brazil, Madagascar, Russia, the United States and other rare-earth localities.
Ytterbium in a xenotime-group lattice
Xenotime-(Yb) is a compact lesson in rare-earth mineralogy: the structure remains familiar while the dominant cation changes the specimen's geochemical identity.
Collecting and care
Protect from acids, impact and dust; retain analytical information because rare-earth dominance cannot be established by appearance alone.
