What is Xianhuaite-(La)?
Xianhuaite-(La) is the lanthanum-dominant counterpart of xianhuaite-(Ce), a rare tetragonal niobium oxide from the Bayan Obo deposit.
Mineralogy and structure
Reference formula: K2LaNb5O15. Xianhuaite-(La) is tetragonal with the ideal formula K2LaNb5O15 and the same tungsten-bronze-type structural family as xianhuaite-(Ce). No matching public COD CIF was selected, so no artificial lattice is shown. Xianhuaite-(La) is classified with oxides and has tetragonal crystal symmetry. Typical hardness is 5–6 on the Mohs scale and specific gravity is approximately 5.1–5.3.
Colour, lustre and habit
Typical colours include brownish red, pale yellow-brown, dark brown. The usual prismatic, granular, massive habit and adamantine, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Xianhuaite-(La) forms in or is associated with rare-earth and niobium-rich alteration zones in a carbonatite-related ore system. Important documented localities include the East Mine of the Bayan Obo deposit in Inner Mongolia, China.
Lanthanum and niobium in a new oxide structure
Xianhuaite-(La) is a specialist species for collectors who follow new mineral discoveries and rare-earth-niobium systems. Provenance is central to its value.
Collecting and care
Protect small grains from impact and acids, and keep the analytical and locality record with the specimen.
