Abstract: An apparatus and process for removing fine particles from sand and other particulate material. The apparatus is generally an air classifier (10) that combines gravitational and aerodynamic forces to classify sand at 10 mesh and finer. According to this invention, the classifier (10) is configured to have a vertical passage (16) centrally located at the vertical axis of an annular-shaped passage (12). The vertical passage (16) is defined by a plurality of inclined vanes (20) that are vertically separated by gaps (28). The sand or other particulate matter is introduced through an inlet (18) at or near the top of the annular-shaped passage (12), and then flows downwardly through the annular-shaped passage (12) around the vertical passage (16).