The particulates of tin tailings slurries sampled from three ex-mining ponds (MN, PN and SH) were mainly clay minerals with some silt and sand particles. The general physical properties of these particulates such as particle size distribution, solids contents and surface area were determined as a function of slime depth and grid position within the ponds. An explanation of the trend observed in terms of the geological origin and formation of the slimes through natural weathering process was attempted. In addition, the particulate nature of the clay minerals was characterized with respect to particle morphology using electron microscopy and clay mineralogy by X-ray diffraction. Analysis on the amorphous and organic contents of the slimes was also included. SH slime with a high amorphous content was acidic in nature whereas PN slime containing about 8% montmorillonite was the most stable colloidally. The stability of these slime dispersions was explained in the light of current theory on lyophobic colloidal dispersions in relation to the clay mineral and chemical compositions of the slime samples. In view of the highly variable particle size and morphology, and considerable variations in exact compositional characteristics of the clay slurries from pond to pond, it is clear that such physicochemical characterization of the slurries is essential in understanding the dewatering behaviour of the slimes and thus important in the subsequent design of an efficient reclamation method most suitable for the pond in question. Because the settling behaviour of the slurry is controlled by colloidal clay, the importance of clay mineralogy in mining waste characterization cannot be overemphasized.