Rare earth-doped hexagonal NaGdF4 nanocrystals were precipitated from a glass. The glass with the mol% composition 70.1SiO(2)center dot 4.3Al(2)O(3)center dot 1.8AlF(3)center dot 2.3Na(2)O center dot 18.5NaF center dot 3.0Gd(2)O(3) doped with 8 x 10(19) Sm3+ ions per cm(3) was already phase separated after casting. The formed droplets enriched in rare earths and fluoride had sizes in the range mainly from 50 to 90 nm. During annealing at temperatures a parts per thousand yen600 A degrees C, multi core particles of hexagonal NaGdF4 were formed inside the amorphous droplet phase. The fluorescence spectra show that Sm3+ is incorporated into the NaGdF4 lattice. This is confirmed by electron dispersive X-ray analyzes performed in a transmission electron microscope.