Great article last week on Phys.org about the Lycurgus Cup. This is a personal story that reminds me of my wife’s wedding ring.
The Romans knew to spike the glass with a few hundred parts million of silver and gold in order to create a dichronic effect.
“The goblet was created approximately 1,600 years ago, using a process whereby very tiny gold and silver particles were embedded in the glass. In normal lighting, the glass appears to have a jade background. When lit from behind, however, the green parts suddenly look ruby red. This is all courtesy of the way electrons vibrate when struck by photons—something the Romans could not have known. Yet, because other goblet pieces have been found with the very same mixture, it’s clear they knew they were on to something. They actually used the color changing effects to create stories. The Lycurgus Cup, for example, depicts the story of King Lycurgus as he is caught up in a tangle of grapevines—penance for treachery committed against Dionysus, the god of wine in Greek mythology.
Researchers speculate that the Romans simply ground the metal particles until it would take a thousand of them to match the size of single sand grain, then mixed them in with the hot liquid glass. But that wasn’t the end of the story: the Romans created a goblet such as the Lycurgus Cup, by carving it from a single block. That means they also understood that different thicknesses of the glass would exhibit different coloring as well.”
Back to me. Instead of buying my wife a diamond ring for our wedding, I got her an Alexandrite stone. However, Alexandrite is a chrysoberyl stone, which has some chromium mixed in to make it into a mood ring. Depending on the lighting, it is either green or red.
