Chalcedony bust of Faustina the Elder (?), wife of the Roman emperor Antoninus Pius. She wears a simple stephane diadem, with a smooth border and without decorations. H. 7.2 cm, w. 5.8 cm
In Medals and Antiques, National Library of France; cameo. 297
pp 406 in CORONAE, STEPHANAI E DIADEMATA Federica Grossi
Tiny garnet bust of Arsinoe II or Berenike II from the Hellenistic Egypt (Alexandria?), 3rd century BCE.
The head is carved in the round and has dimensions: 1.8 × 1.5 × 1.5 cm.
In The Getty Museum
“The cameo depicts Antonia wearing a veil and a diadem in the guise of a priestess of the cult of the deified Augustus. Stars and a portrait of Augustus wearing a laurel wreath decorate the diadem. The cameo was probably carved after Antonia’s death in A.D. 37, during the reign of her son Claudius, the fourth Roman emperor.”
White chalcedony; Italy, Roman, 41-54 CE; 5 cm, w. 2.8 cm
Chalcedony portrait bust of Antonia Minor, a niece of the Emperor Augustus. The most interesting is her stephane diadem typical of a priestess of the Augustus cult, with the imprint of a gem depicting a head of Apollo-Augustus crowned with a laurel wreath, and surrounded by stars.
additional source: CORONAE, STEPHANAI E DIADEMATA Federica Grossi, pp. 349
British Museum 
British Museum
Green chalcedony (plasma) portrait bust one of the women: of the Agrippina Younger, wife of the Emperor Claudius and mother of the Emperor Nero, Julia Livilla, Julia Drusilla. Roman, 1st century.
“The bust is carved in the round with the remarkable skill typical of imperial cameos of the Julio-Claudian era. The flesh is highly polished to contrast with the matt surface of the hair with its mass of engraved detail. The empress’s hairstyle was copied by many subjects of mummy portraits and gilded masks.”
In the British Museum inv. GR 1907.4-15.1 (Gem 3946)
See also my posts: