Chrysoberyl is composed of beryllium aluminum oxide and is colorless when in its pure form. Trace amounts of iron color the mineral yellow (as seen here), brown, and green. Chrysoberyl is an extremely hard and durable mineral. It is most commonly found as greenish-yellow crystals. Although better known for the rare and valuable cat's eye and alexandrite varieties, chrysoberyl is also cut into such attractive gems as this 114.25 carat stone from Minas Gerais, Brazil.