The velocity acquired by a particle in descending a roughened inclined chute is a measure of 3-dimensional particle shape. This principle is embodied in an automatic device for classifying coarse sand grains into 3 shape classes: spherical, intermediate, and tabular. Six samples of 1500 grains each can be classified in 2.5 hours. Tabularity, a particle property of significance in settling velocity work, is the geometric shape attribute that most strongly affects particle descent velocity in a chute. That this attribute is geologically significant is suggested by the emergence of well-defined sub-regional patterns of particle shape distribution.