There are two varieties of the mineral chrysoberyl which exhibit simultaneously unusual and beautiful phenomenon in the finest examples: the cat's eye and the alexandrite. The latter is the most coveted, and arguably the most remarkable. The present alexandrite is a particularly fine specimen as can be seen from the comment on the Gbelin certificate accompanying the stone. The gem originated in Brazil where mining is undertaken in the States of Minas Gerais, Espirito Santos and Bahia. Its superb colour change is caused by the presence of chromium oxide. In examining the two illustrations, one can observe that daylight, which emphasizes the blue end of the spectrum, renders this particular crystal a lovely teal green. Yet, when exposed to electric light, or that of a candle, both rich in red rays, it appears an attractive plum-like red.