For the potential applications in hot-gas filtration/catalysis, porous mullite bodies were prepared by simply calcining natural topaz powder compacts with or without porosity control media at 1300 o C. Interconnected pores (28-80% porosity) and needle-like mullite crystals (up to 10 μm long and <1 μm thick) were two intrinsic microstructural features associated with the decomposition of topaz to form mullite phase.