Researchers have finally found out why the jade-green cup
appears red when lit from behind
The colorful secret of a 1,600-year-old Roman chalice at the
British Museum is the key to a supersensitive new technology that might help
diagnose human disease or pinpoint biohazards at security checkpoints.
The glass chalice, known as the Lycurgus Cup because it
bears a scene involving King Lycurgus of Thrace, appears jade green when lit
from the front but blood-red when lit from behind—a property that puzzled
scientists for decades after the museum acquired the cup in the 1950s. The
mystery wasn’t solved until 1990, when researchers in England scrutinized
broken fragments under a microscope and discovered that the Roman artisans were
nanotechnology pioneers: They’d impregnated the glass with particles of silver
and gold, ground down until they were as small as 50 nanometers in diameter,
less than one-thousandth the size of a grain of table salt. The exact mixture
of the precious metals suggests the Romans knew what they were doing—“an
amazing feat,” says one of the researchers, archaeologist Ian Freestone of
University College London.