Prasio. Lo Smeraldo degli Imperatori. Prase: the Emperors' Emerald

In both ancient and modern texts, the terms prase, plasma, chrysoprase, emerald, and emerald root, to name but a few, are all used to refer to just one gemstone:Chrome Chalcedony. This paper aims to resolve not only the linguistic debate around this green gemstone, often used in glyptics to portray emperors, mythological characters and leaders, but also that around its geographical and temporal origins, and the value attributed to it. Their historical, literary and museum research, combined with the gemmological analyses of a rich sample of archaeological prases, has led the authors to hypothesise that these fascinating green gemstones come from the island of Cyprus.