Valued for thousands of years, chrysoberyl is a surprising gem that you'll love as much for what it does as for how it looks. Chrysoberyl is an action gem, changing and moving in response to light. In the gem world, these special effects are known as phenomena. The gem varieties of chrysoberyl respond to light in surprising ways.
The best-known special effect of chrysoberyl is an eye, which is displayed when certain specimens of this gem are cut in a dome shape. Cat's-eye chrysoberyl has a pupil-like band of light that sweeps across its dome. The "eye" is caused by fibrous inclusions that reflect the light in a sharply defined pattern. The effect is uncanny and quite cat-like. Although other gem varieties can display this effect, none is as dramatic.