Pottery pipes with flaring bowls and slender stems, sometimes as much as eighteen inches long, are found in prehistoric Caddoan sites in Arkansas. The stems are excessively fragile, and as these pipes are usually found in the corners of graves, it seems probable that they were made for mortuary use rather than actual smoking. They are clearly imitations of a type which had a corn-cob bowl impaled on a reed stem. Stone pipes occur over a wider territory than pottery pipes and show a greater diversity of form. There are some regions in which the same shapes occur in both stone and pottery, but there are several types of pipe which appear never to have been made of clay. Most of the stones used in pipe-making were quite soft, but a few pipes of quartzite and other hard rocks have been found. The material was carefully selected, and was usually obtained from regular quarries. In the eastern United States steatite, serpentine and slate were the stones most used. In the upper Mississippi valley and Great Plains the favorite material was catlinite, a fine-grained claystone soft enough to be easily worked with stone tools, but firm enough to take a high polish. Deposits of this material have been found in several states, and a local variety was used by the Ohio Mound Builders. The most famous catlinite quarries are in southeastern Minnesota and yield the highly prized red stone from which so many Plains Indian pipes are made. Here the catlinite occurs as a narrow layer, nowhere more than twenty inches thick, between strata of compact quartzite five to eight feet thick. To reach the catlinite it was necessary to break away the quartzite with stone mauls or shatter it by building large fires upon it and then dashing water on the heated stone. The old Indian workings extend for more than a mile along the face of the deposit, and the quarry must have been in use for several centuries. According to Indian traditions, the place was visited by many different tribes, who considered it common property and abstained from hostilities there. In historic times the Dakota considered it exclusively their property, and part of it was set aside for their use when they ceded their other lands in the vicinity. They still visit it occasionally to obtain stone for their pipes. White men have also worked the quarry, and in 1865 and 1866 over two thousand pipes of this material were made by the Northwestern Fur Company for their trade with the Indians.