This Alexandrite ring changes color with the light. It is surrounded by a round cut halo of 30 diamonds with a total weight of 30ct. The lab grown Chatham Alexandrite is an emerald by day, ruby by night. Alexandrite's are a rare variety of the mineral chrysoberyl that changes color from bluish-green in daylight to purplish-red in incandescent light. The stone was discovered in 1830 and named after Czar Alexander II.