Abstract: A mechanically strong, thermally stable porous siliceous pellet having a high pore volume and surface area with a major portion of the pore volume in pores of radii more than 20 Angstroms and the process of producing the pellets by shaping a clay, acid-leached to a degree insufficient to destroy the plasticity of the clay, forming the leached clay into shaped particles, calcining the particles and further extracting the calcined clay pellets without impairing their shape.