When light strikes the Lycurgus Cup, it scatters off of the tiny (nano-sized) gold and silver particles. This optical scattering causes the reflected light to appear jade green and the transmitted light to appear red, when the cup is filled with air.

What is the use of Lycurgus Cup?

The cup shows the mythical King Lycurgus, who (depending on the version of the myth) tried to kill Ambrosia, a follower of the god Dionysus. She was transformed into a vine that twined around the enraged king and restrained him, eventually killing him.

What does the imagery on the Lycurgus Cup represent?

It represents a type referred to as 'cage cups' (diatreta) and belongs to a rare group of dichroic glass. It depicts the punishment of king Lycurgus for his hubris against Dionysus. ... The Lycurgus Cup represents another rare group, which is called dichroic glass.