The physical and mechanical properties of the dielectric materials mainly depend on shapes of particles in granular media. In order to reveal the differences of physical and mechanical properties between tailings and natural sands from the microscopic view, the usage of digital image processing techniques contributes to the quantification of shape descriptors (elongation, sphericity, convexity, and roughness) describing the shapes of particles. The comparison between four tailings (gold, tin, copper, and iron) and two natural sands (river sand and sea sand) is made in the current study. Results show that particle shape descriptors have great relationship with particle size. The decrement of particle size, on one hand, leads to the increase of the elongation of tailings and sea sand, and thus forming the needle-like or columnar shape of particles. The sphericity of tailings and river sand also increases and generates spherical shapes of particles. On the other hand, both of the convexity and roughness of tailings and sea sand grow with larger particle size. The remarkable difference can be observed on surface texture of particles between tailings and sea sand. Much higher angularity of tailings is also represented by comparing with that of sea sand and river sand.