Rare Roman intaglio in emerald presenting the profile portrait of a character wearing a laurel wreath in his hair, most certainly the God Apollo, mounted in a ring (in solid gold), intaglio probably from the 3rd-4th century. ap. JC.
This intaglio is in good condition and is of remarkable quality. The ring is in solid gold (tested), mounting made later.
A note: micro-chips, scratches and wear of time, see photos.
Emeralds were particularly rare during antiquity. They came mainly from Egypt, although there are also some ancient deposits in India. They are still quite opaque. Emeralds were particularly fashionable in the Roman Empire from the 3rd century CE.