Mn-doped zinc orthosilicate (Zn2SiO4)-bearing phosphor microparticles were synthesized with controlled three-dimensional (3-D) morphologies inherited from the microshells (frustules) of diatoms (unicellular algae). Silica-based diatom frustules were first coated with manganese and zinc oxide nanoparticles by exposure to an acetate precursor solution and then firing at 700 degrees C. Subsequent reaction of the nanoparticles with the underlying silica at 1050 degrees C yielded compact, continuous, and conformal Mn-doped Zn2SiO4 coatings on the frustule surfaces. The converted 3-D microparticles exhibited bright green emission upon stimulation with 275-nm light. Photoluminescent microparticles with a wide variety of well-controlled 3-D morphologies can be mass produced with this simple, low-cost bioclastic process.