From the Greek Khrysos meaning “gold” and beryllos meaning “bright stone”, chrysoberyl is a blue-tinted green-yellow to yellow-brown stone, which has been known since ancient times. Two very rare varieties of chrysoberyl are much sought-after today. These are alexandrite, which is green in daylight but red in artificial light, and cat’s eye whose specific structure creates an optical phenomenon known as chatoyancy. Certain exceptional chrysoberyls
can be seen in museums, such as the Hope (not to be confused with the diamond of the same name), a light green chrysoberyl weighing 45 carats that is part of the British Museum collections. Beryllium aluminium oxide. Hardness: 8.5. Sri Lanka, Brazil.