This body is a plastic fireclay base having 13% 20/48 grog and 10% 65 mesh silica sand. But the texture is far coarser than one would expect. That is because it has 4 cubic feet of perlite per thousand pound batch. If desired the surface can be trowel smooth. This works well partly because the perlite particles are soft and easy to crush.
In ceramics, clays with added aggregate are free formed or molding into shapes that are slowly dried and fired in a kiln. The process requires much skill.
Grog is a term used in ceramics to describe crushed brick (or other fired ceramic) aggregate that is added to sculpture and structural clays to improve drying properties.