This picture shows all four sides of a hemisphere that was found several years ago in a cultivated field in St. Clair County, Illinois. It's a better than average example. It was uniformly pecked into shape with a hammerstone the same way axes and celts were made. The surface was then polished and further shaped by grinding against an abrasive stone using water as a lubricant. This hemisphere was made from granite and it measures 1 5/8 inches (4.1 cm) long, 1 1/4 inches (3.2 cm) high and 1 1/16 inches (2.7 cm) thick.