Sandstone grinding slab from McMullen County vicinity, both sides shown. This material is relatively hard and well-cemented with fairly coarse sand grains. At the top is the working surface, a slightly concave ground surface upon which nuts or seeds or other plant products were reduced to meal. Note also the linear grooves from presumably later use of this artifact for abrading. At the bottom is the natural unmodified surface which retains traces of calcium carbonate, probably from its original geological context. Brom Cooper Collection, TARL