The luminescence properties of the compounds LaPO{sub 4}:Cr and LaMgB{sub 5}O{sub 10}:Cr at 4.2 K are reported. Furthermore, the morphology of these compounds has been studied with a high-resolution transmission electron microscope (HRTEM). The Cr{sup 3+} ion shows a Stokes-shifted broad-band emission in the near-infrared region which is attributed to the {sup 4}T{sub 2}{r_arrow}{sup 4}A{sub 2} transition. It is concluded that the Cr{sup 3+} ion is not built-in into either LaPO{sub 4} or LaMgB{sub 5}O{sub 10} but is present in an amorphous surface layer. The amorphous second phase is observed in HRTEM images. 22 refs., 6 figs.