The street curbs in the oldest parts of San Francisco were initially made from cut blocks of granite. These are gradually disappearing. Whenever an old sidewalk has to be torn out, the curbs of the new sidewalk are of course made of concrete. Whether anybody makes any use of the torn-out slabs of granite I do not know. In the picture immediately above, taken near Mission Dolores, the section of curb on the left-hand side is granite and that on the right-hand side is concrete.