The "gem of Augustus" can be found at present in theCabinet des Médaillesof France'sBibliothèque Nationale. This ornament is said to have been admired in particular by the painter Rubens. It was carved from Arabian onyx between 10 and 20 years after the birth of Christ. Image source is here. The thoughtfulness of the portrait is unexpected, set against such a flamboyant surround.