Origin of an Emerald Cabochon from a Roman Estate at Gerace, Sicily

Abstract The late Roman rural estate of Gerace is located in Sicily’s Enna province. Between 2016 and 2019, excavations focused on a bathhouse (ca. 380 AD) approximately 50 m northeast of the main villa. During excavation of the fill in a tepidarium (warm room) in 2017, an emerald cabochon was discovered. The cabochon is medium green, translucent to opaque, round in outline with a flat back, 9 mm in length and 4 mm high, and weighs ∼2.5 ct. In Roman times, emeralds enjoyed great popularity in jewelry, and the cabochon’s shape, size, and flat base all suggest that this example was lost from a ring. A tiny fragment of material from the back surface of the cabochon was fashioned into a polished mount for origin determination. Three EPMA major element compositions were compared to 264 literature values for world emerald localities, but the results were inconclusive. Two LA-ICP-MS trace element compositions were compared to 575 analyses of comparison samples, mainly from the Gemological Institute of America. In trace element compositional graphs, the Gerace emerald plots close to or within a field encompassed by points representing compositions of reference samples from Egypt. Linear discriminant analysis was used to compare the two LA-ICP-MS analyses of the Gerace sample to 561 analyses of the comparison samples; the results show an average 98.24% probability that the Gerace emerald is from Egypt. This determination is bolstered by the presence of a F-rich phlogopite inclusion in the sample fragment, suggesting a Type IA emerald deposit. The Gerace emerald was undoubtedly obtained from one of several emerald extraction sites known in the southern part of the Eastern Desert in Egypt. We can surmise that the raw material was transported by caravan to Apollonopolis Magna (modern Edfu) or Koptos (modern Qift) on the Nile River, then by boat to a Mediterranean city (Rome?), where it would have been fashioned into a cabochon ready for sale. This study illustrates how origin determination, of increasing importance to the gem trade, also throws light on commercial contacts within the Roman Empire.