Roman amethyst gem with the bust of Athena / Minerva (the goddess of war and wisdom) from the 1st – 2nd century A.D.

She wears a Corinthian helmet adorned with a long plume and her chest is protected by the aegis, the goatskin shield her father Zeus gave her.

At the bottom center of the aegis, the artist placed the head of Medusa (the gorgoneion) wreathed with coiling snakes.

(For scale, the dimensions are ~1.8 x 2.5cm)