This is a purple glass amethyst colored seal from bronze age Mesopotamia/Sumeria. It is oblong in shape with a hole in the middle, to be hung on a string as a bead.

A cylinder seal is a cylinder engraved with a "picture story," used in to roll an impression onto a two-dimensional surface, generally wet clay. Scholars believe that cylinder seals date from circa 3500 BCE in the Near East; the earliest known seals come from the contemporary site of Susa in south-western Iran and at the early site of Uruk in southern Mesopotamia. They are linked to the invention of cuneiform writing on clay cylinders.