This investigation, using the scanning electron microscope (sem) to ascertain the size, shape, and texture of solid particles and aggregates in the Florida phosphate slimes, has shown that the shape of the particles is of great significance in influencing the rate of settling, or nonsettling, of the solid particles having diameters less than a few micrometers. Settling is most strongly inhibited in suspensions in which the solid component is composed of, or contains a major proportion of, fibrous hairlike crystals such as those of the attapulgite variety of palygorskite. The interlocking and mutually supporting fibers, as clearly seen in some of the sem photographs, indicate that they have sufficient strength to support their own weight and that of the particles above them. However, the possibility that some other factors, such as electrical or molecular forces, may be significant has not been eliminated. Fifteen samples were studied and photographed with the sem. The slender hairlike forms of attapulgite were predominant in samples from which the solid materials settle more slowly.