Alexandrites are mined in Russia and change color depending on the light source. The sought after stones turn green in daylight and red in incandescent light. Alexandrites were named in honor of the young Tsar Alexander II. The stone is usually found in small sizes under 1.00 ct., rarely is it seen over 5.00 cts. There are three alexandrite lots coming up in the fine jewelry sale including lot 579, which is an Edwardian alexandrite and diamond pendant/brooch, set with a cushion-cut alexandrite of approximately 7.27 carats, estimated at $10,000 to $15,000. Lot 580 is an Edwardian alexandrite and diamond ring, set with a cushion-cut alexandrite weighing approximately 7.67 carats, and is estimated at $10,000 to $15,000. The sale features a number of signed contemporary pieces, notably from Gianmaria Buccellati including lot 431, a gem-set flower brooch, set with an old mine-cut diamond weighing approx. 1.20 cts., further set with a fancy cut sapphire and ruby, cabochon emerald highlights,

Source: News-antique.com (press release)