A cylinder seal is a small round cylinder, typically about one inch in length, engraved with written characters or figurative scenes or both, used in ancient times to roll an impression onto a two-dimensional surface, generally wet clay. Cylinder seals were invented around 3500 BC in the Near East, at the contemporary sites of Susa in south-western Iran and Uruk in southern Mesopotamia. They are linked to the invention of the latter’s cuneiform writing on clay tablets. They were used as an administrative tool, a form of signature, as well as jewelry and as magical amulets; later versions would employ notations with Mesopotamian cuneiform. In later periods, they were used to notarize or attest to multiple impressions of clay documents. Graves and other sites housing precious items such as gold, silver, beads, and gemstones often included one or two cylinder seals, as honorific grave goods.
The seals themselves are typically made from hardstones and some are a form of engraved gem, but they may use glass or ceramics such as Egyptian faience. Many varieties of material such as hematite, obsidian, steatite, amethyst, lapis lazuli and carnelian were used to make cylinder seals. As the alluvial country of Mesopotamia lacks good stone for carving, the large stones of early cylinders were imported probably from Iran. Most seals have a hole running through the centre of the body, and they are thought to have typically been worn on a necklace so that they were always available when needed.
While most Mesopotamian cylinder seals form an image through the use of depressions in the cylinder surface, some cylinder seals print images using raised areas on the cylinder (see San Andrés image, below, which is not related to Mesopotamian cylinder seals). The former are used primarily on wet clays; the latter, sometimes referred to as roller stamps, are used to print images on cloth and other similar two dimensional surfaces.
Cylinder seals are a form of impression seal, a category which includes the stamp seal and finger ring seal. They survive in fairly large numbers and are often important as art, especially in the Babylonian and earlier Assyrian periods. Impressions into a soft material can be taken without risk of damage to the seal, and they are often displayed in museums together with a modern impression on a small strip.