xenotime, widely distributed phosphate mineral, yttrium phosphate (YPO4), though large proportions of erbium commonly replace yttrium), that occurs as brown, glassy crystals, crystal aggregates, or rosettes in igneous rocks and associated pegmatites, in quartzose and micaceous gneiss, and commonly in detrital material. Occurrences include Norway, Sweden, Madagascar, Brazil, and North Carolina. The name is from the Greek word meaning “vain honour,” because the yttrium in xenotime was mistakenly thought to be a new element. For detailed physical properties, see phosphate mineral (table).