Periodisation

Imperial Roman jewellery covers the period from the establishment of the Principate under Augustus in 27 BCE through the dissolution of the western empire in the late fifth century CE. The category is conventionally divided into early Imperial, from Augustus through the Antonines to roughly 192 CE, middle Imperial through the Severan dynasty and the third-century crisis to roughly 285 CE, and late Imperial through the Tetrarchy and the Constantinian and post-Constantinian dynasties to the formal western collapse. The eastern continuation, the Byzantine tradition, properly belongs to a separate stylistic discussion although there is significant overlap in the fourth and fifth centuries.

Materials and supply

The Roman empire absorbed the gemstone supply networks of the Hellenistic kingdoms it conquered and added Indian, Arabian and East African production to the existing Mediterranean supply. The principal materials were gold, silver, electrum, garnet, emerald, sapphire, peridot, amethyst, beryl in the green and yellow varieties, chalcedony, agate, sardonyx, coral, pearl, amber from the Baltic, jet from Britain, and freshwater pearl from the British and Continental rivers.

Indian goods entered through the Red Sea ports and the Periplus Maris Erythraei trade route. Pliny the Elder's Natural History, Book 37, written in the late first century CE, is the principal contemporary source on the Roman gem trade and lists the materials by source and price, with the most expensive being adamas, the term used for diamond and probably also for some other very hard transparent stones. Pliny's prices are notable for being given in terms that allow comparison: a fine pearl could exceed the value of an estate, a diamond was beyond the means of all but the wealthiest senators, and amber was a luxury substantial enough that Nero's expedition to the Baltic to secure supply was politically noteworthy.

Forms and techniques

The Imperial Roman jewellery vocabulary differs from the Hellenistic predecessor in scale and in the consistent use of polished cabochon and faceted gemstones rather than the cameo and intaglio focus of earlier periods. Imperial pieces include bracelets in serpentine and rigid forms, neck chains in loop-in-loop and box-link constructions, fibulae in increasingly elaborate forms, finger rings with set stones, and earrings in pendant and hoop forms. Diadems for women of the imperial family appear in surviving sculpted portraits and in fragmentary archaeological survivals.

Setting techniques include the bezel, with the gemstone seated in a collar of metal closed over its perimeter, and the box setting, with the stone set in a constructed cell. Open-back settings for transparent stones became standard in the second century CE, allowing light transmission through emerald and sapphire. Granulation and filigree, inherited from Etruscan and Hellenistic practice, decline in technical refinement through the Imperial period as the workshop tradition concentrated on production scale rather than virtuoso fine-grain work.

The cameo and intaglio tradition

The carved hardstone cameo, in sardonyx, agate and chalcedony, reached its imperial peak in the first and second centuries CE. The Gemma Augustea, a two-layer onyx cameo nineteen by twenty three centimetres, depicting Augustus in apotheosis, is the largest and most celebrated surviving Roman cameo and is held at the Kunsthistorisches Museum Vienna. The Great Cameo of France, a five-layer sardonyx cameo thirty one by twenty six centimetres, depicting the Julio-Claudian dynasty, is held at the Bibliothque nationale de France in Paris. These pieces represent the apex of the Roman lapidary tradition and have no later parallel in scale or execution.

Intaglio gem engraving, in which the design is cut into the surface of the stone for use as a seal impression, continued throughout the period and was the principal personal-identifier technology of the empire. The intaglio gem mounted in a finger ring, the signum, served as the legal signature of every literate Roman of free status. Surviving intaglios number in the tens of thousands across European museum collections and remain the most accessible category of Imperial Roman gem material in the modern trade.

The emerald and the Mons Smaragdus

The Roman supply of emerald came principally from the Mons Smaragdus, the Smaragdus mountains, in the Eastern Desert of Egypt, mined from the Ptolemaic period and intensively from the early Imperial period through the late fourth century CE. The deposit, rediscovered archaeologically in the early nineteenth century, is the world's principal pre-Columbian emerald source. The Roman emeralds were of moderate to good colour and clarity but did not reach the saturation of Colombian Muzo material, which was unknown to the Roman world.

The mining settlements at Sikait and Nugrus, in the Egyptian Eastern Desert, are now archaeological sites with substantial preserved infrastructure. The Roman demand absorbed essentially all the production of the deposit through the imperial period.

The diamond question

The Roman knowledge of diamond is documented but limited. Pliny describes adamas as the hardest known substance, gives sources in India, and notes the use of diamond points to engrave other gemstones. Surviving Roman diamond use is restricted to small uncut crystals set in rings, with no faceting before the late medieval period. The diamond's place in Roman jewellery is therefore peripheral despite its conceptual importance.

The pearl economy

Pearls, by contrast, dominated the high-end Roman market. Cleopatra's pearl, the celebrated stone she reputedly dissolved in vinegar to win a wager with Mark Antony, was reported to be worth ten million sesterces, an enormous sum equivalent to the annual revenue of a small province. Whether the dissolution actually occurred or whether Pliny's account is moralistic literary embellishment, the price reported is a useful index of high-end pearl valuations in the period.

The principal pearl supply came from the Persian Gulf and the Indian Ocean, traded through the same Red Sea routes that delivered other Indian luxury goods. Roman saltwater pearl jewellery survives principally in Egyptian and Levantine archaeological contexts, where the dry climate has preserved organic material that would not have survived in northern European burial sites.

The late imperial transformation

From the third century CE onward, Imperial Roman jewellery undergoes a stylistic transformation toward greater colour saturation, larger gemstones in more visible settings, and a vocabulary of openwork gold combined with coloured stones that anticipates the Byzantine. The Hoxne Hoard in Britain, dated to the early fifth century, and the Trsor de Beaurains in northern France, dated to the late third century, are principal archaeological references for late Imperial gold and gem jewellery. The Christianisation of the empire from Constantine onward introduced cross-form pendants, biblical-scene cameos, and ecclesiastical regalia that bridge into the Byzantine period.

The modern market

For the working trade, Imperial Roman jewellery comes principally from archaeological contexts and is regulated by national and international heritage law. The 1970 UNESCO Convention on the Means of Prohibiting and Preventing the Illicit Import, Export and Transfer of Ownership of Cultural Property is the principal framework. Major auction houses require provenance documentation tracing pieces to before 1970 or to legal export permits, and the market for unprovenanced Imperial Roman jewellery has contracted sharply in the past two decades as enforcement has tightened.

Roman intaglios, by their abundance, remain accessible at moderate prices, with documented pieces from old European collections trading in the hundreds to low thousands of US dollars at fine-art auction. Imperial gold jewellery with documented pre-1970 provenance trades at substantially higher levels, with rare pieces in the high tens to low hundreds of thousands. Cameos of major historical importance trade only at institutional or estate level and rarely come to public market.