What is Xenotime-(Gd)?
Xenotime-(Gd) is the gadolinium-dominant member of the xenotime group, a rare-earth phosphate found in pegmatites and high-temperature geological systems.
Mineralogy and structure
Reference formula: GdPO4. Xenotime-(Gd) is tetragonal and isostructural with xenotime-(Y). The guide uses a clearly labelled xenotime-(Y) representative model because no separate Gd-dominant public COD CIF was selected. Xenotime-(Gd) is classified with phosphates and has tetragonal crystal symmetry. Typical hardness is 4–5 on the Mohs scale and specific gravity is approximately 4.3–4.8.
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-(Gd) forms in or is associated with granitic pegmatites, alkaline rocks, hydrothermal veins and heavy-mineral concentrates. Important documented localities include rare-earth pegmatites in Scandinavia, Brazil, Madagascar, Russia and the United States.
Gadolinium in the xenotime structure
Xenotime-(Gd) is a specialist rare-earth mineral whose value comes from authenticated chemistry, crystal form and pegmatite provenance rather than polished appearance.
Collecting and care
Protect from acids and impact; preserve the host-rock context and do not infer rare-earth identity from colour alone.
