the proppant is a granular material that prevents the created fractures from closing after the fracturing treatment. types of proppant include silica sand, resin-coated sand, bauxite, and man-made ceramics. the choice of proppant depends on the type of permeability or grain strength needed. in some formations, where the pressure is great enough to crush grains of natural silica sand, higher-strength proppants such as bauxite or ceramics may be used. the most commonly used proppant is silica sand, though proppants of uniform size and shape, such as a ceramic proppant, are believed to be more effective.