Summary: A number of new alkaline-earth-rare-earth silicate and germanate compounds with the apatite-type structure have been synthesized including a new calcium lanthanum silicate, Ca₄La₆(SiO₄)₆(OH)₂, which has a 9·63 Å, c 7·12, and c/a 0·740. This has a random distribution of Ca²⁺ and La³⁺ over the (4f) and (6h) sites in the lattice. X-ray data are given for Ca₄La₆(SiO₄)₆(OH)₂ together with cell dimensions for other synthetic silicate and germanate apatites. Silicate apatites with partially occupied or vacant halogen (2a) sites analogous to those of the pyro- morphites have been prepared, and a classification for silicate apatites based on synthetic end-members is proposed.