Stone tools and the by-products of making them are the longest lasting and most common artifacts archaeologists encounter. By this time, tool production was a specialized craft, and Mississippian stoneworkers created utilitarian and ritual artifacts marked by extraordinary craftsmanship and consistency of form. Drills, knives, arrow points, and spear points were made by chipping fine-grained chert and other rock. Stone pipes, grooved and ungrooved axes, gaming pieces, and pendants were made by pecking, grinding, drilling, and polishing raw stone. The people of Aztalan used local stone to produce many items, but some tools, such as hoe blades, were made from cherts available only in southern Illinois. These tools may have been acquired through trade or brought to the site by Aztalan's Mississippian immigrants.