This translucent yellow-green chrysoberyl owes its name to a beautiful optical phenomenon caused by the nature of its tubular inclusions which are revealed when the stone is cut as a cabochon: its blue-tinted opalescence is accompanied by moving streaks of light, similar to the pupil of a cat’s eye.
In ancient times it was known as cymophane meaning “wave-like”.
A similar effect can be produced by other stones when cut as cabochons.
However, in this case the term cat’s eye must be preceded by the name of the mineral, e.g. tourmaline cat’s eye, quartz cat’s eye, etc.
Beryllium and aluminium oxide. Hardness: 8.5. Birthstone of Capricorn. Brazil, Sri Lanka.