The art of glyptics, or carving images on colored precious stones, is probably one of the oldest known to humanity. Intaglios, gems with an incised design, were made as early as the fourth and third millennia B.C. in Mesopotamia and the Aegean Islands. They exhibit a virtuosity of execution that suggests an old and stable tradition rooted in the earliest centuries. The tools required for carving gems were simple: a wheel with a belt-drive and a set of drills. Abrasives were necessary since the minerals used were too hard for a metal edge. A special difficulty of engraving intaglios, aside from their miniature size, was that the master had to work with a mirror-image in mind.
Achelous was the name of the largest river in Greece, (presently Aspropotamo, flowing into the Ionian Sea), named after a son of Poseidon. Having once been mortal, Achelous was crossing a river when bit by an arrow. Falling into the water he was transformed into a deity who could change into many different forms. In a contest for the band of beautiful Deianeira, Achelous and Hercules waged a bitter battle. In the course of the struggle the river god changed himself into a bull. Hercules managed to tear off one of the horns, causing Achelous to concede victory. It is in the guise as bull we see this allusive deity. The image is based on a stater from the city of Thyrrheion (east of Anaktorian, Greece), dated 350 - 250 BC. The cameo even bears the same Greek inscription spelling out the name of Achelous. From the glowing carnelian an image from the fascinating and mysterious Greek myths comes alive.