gems, artificial glass, chrome chalcedony, emerald, beryl, non-destructive techniques, Roman jewellery

The study of gems in Roman-period jewellery from known archaeological contexts offers valuable insights into ancient gem trading routes, manufacturing and decoration techniques, and the popularity or association of specific gems with certain jewellery types. Accurate identification of these gems also enhances the museum’s ability to inform the public. In this study, 19 green-coloured gems embedded in 14 Roman jewellery pieces—dated between the first and fourth centuries CE and held by the Archaeological Museum of Thessaloniki in Greece—were examined. Most of the pieces were discovered during rescue excavations in Roman cemeteries in western and eastern Thessaloniki, with one originating from Edessa in northern Greece. Non-destructive techniques such as optical microscopy, Raman spectroscopy, and Vis-NIR spectroscopy were employed, along with micro-EDXRF for chemical analysis. Seventeen of the samples were identified as natural emeralds resembling those from Egypt, while the remaining two were identified as a natural chrome chalcedony and an artificial glass. The origin of the artificial glass remains unknown, while the chrome chalcedony is tentatively linked to Turkey.