Lot Essay
Alexandrite (a variety of chrysoberyl) was first found in the Takovaya River near Ekaterinburg, a town close to the Ural Mountains, in 1830. The gem was named after Czar Alexander II who celebrated his twenty-first birthday on the very day that the first specimen was discovered.
They are also found in Sri Lanka. Although they are often larger, they rarely show such a marked colour change when compared with those originating from Russia. More recently, the gem has also been mined in Burma, Brazil, Madagascar and Zambia.
The extraordinary change in colour in these gems is due to the manner by which light is absorbed. The transmission of the red and blue-green part of the spectrum are just about equal and therefore any change in the colour of light will emphasize one or other of the spectral colours. In daylight, which tends to contain more blue light, the shade tips towards the blue-green end of the spectrum and consequently the stone appears more green. However, in artificial light (or next to a lighted match), an alexandrite will appear redder. The colour change is augmented by the fact that they demonstrate remarkable pleochroism.
They are also found in Sri Lanka. Although they are often larger, they rarely show such a marked colour change when compared with those originating from Russia. More recently, the gem has also been mined in Burma, Brazil, Madagascar and Zambia.
The extraordinary change in colour in these gems is due to the manner by which light is absorbed. The transmission of the red and blue-green part of the spectrum are just about equal and therefore any change in the colour of light will emphasize one or other of the spectral colours. In daylight, which tends to contain more blue light, the shade tips towards the blue-green end of the spectrum and consequently the stone appears more green. However, in artificial light (or next to a lighted match), an alexandrite will appear redder. The colour change is augmented by the fact that they demonstrate remarkable pleochroism.