Iconography
The iconography of gems is similar to that of coins, though more varied. Early gems mostly show animals. Gods, satyrs, and mythological scenes were common, and famous statues often represented - much modern knowledge of the poses of lost Greek cult statues such as Athena Promachos comes from the study of gems, which often have clearer images than coins. A 6th(?) century BC Greek gem already shows Ajax committing suicide, with his name inscribed. The story of Heracles was, as in other arts, the most common source of narrative subjects. A scene may be intended as the subject of an early Archaic gem, and certainly appears on 6th century examples from the later Archaic period.
Portraits of monarchs are found from the Hellenistic period onwards, although as they do not usually have identifying inscriptions, many fine ones cannot be identified with a subject. In the Roman Imperial period, portraits of the imperial family were often produced for the court circle, and many of these have survived, especially a number of spectacular cameos from the time of Augustus. As private objects, produced no doubt by artists trained in the tradition of Hellenistic monarchies, their iconography is less inhibited than the public state art of the period about showing divine attributes as well as sexual matters. The identity and interpretation of figures in the Gemma Augustea remains unclear. A number of gems from the same period contain scenes apparently from the lost epic on the Sack of Troy, of which the finest is by Dioskurides (Chatsworth House).
Renaissance and later gems remain dominated by the Hellenistic reportoire of subjects, though portraits in contemporary styles were also produced.
Read more about this topic: Engraved Gem