The Roman Lycurgus Cup glows green in daylight and ruby red when lit from behind, thanks to gold
The 4th-century Roman Lycurgus Cup in the British Museum turns from green to ruby red when lit from behind, thanks to tiny gold and silver particles.
British Museum
Roman color-changing glass may be repeatable again; Sheffield team grew gold and silver nanocrystals in a melt
The Lycurgus Cup holds roughly 330 parts per million of silver and 40 of gold. A University of Sheffield replica goes on show in a new sculpture from November 6.