Alexandrite

Alexandrite (Chrysoberyl) Gemstones

• Hardness

  8.5.
  

• Occurrence

  United States, Russia (Ural Mountains), Sri Lanka (Ceylon), Zimbabwe (Rhodesia), Brazil, Madagascar, Italy.
  

• Appearance

  Named after the Russian Czar, Alexander II, alexandrite is the gemstone most noted for it's color changing abilities. Colors are greenish outdoors, and reddish to violet under artificial light. Alexandrite is extremely rare. Look out for alexandrite which is too clean, or at a price which seems too low, it's probably synthetic. Natural alexandrite rarely exceeds 2 carats. Can be confused with synthetic alexandrite, or synthetic color change corundum. Pearl, moonstone and alexandrite are the birthstones of the month of June. Photographs have been retouched to show the approximate color change from indoors to outdoors.
  

• Enhancements

  Alexandrite is not enhanced.
  More information on gemstone enhancements.
  

• Gemstone Family

  Alexandrite is a member of the Chrysoberyl gemstone family.

• AAA Deeper green to bluish green, nearly eye-clean, bright to high color change.
• AA Green to greenish blue, slightly included, moderate to medium color change.
• A Light green to greenish blue, included, weak to low color change.

          The alexandrite variety displays a color change (alexandrite effect) dependent upon the nature of ambient lighting. Alexandrite effect is the phenomenon of an observed color change from greenish to reddish with a change in source illumination due physiological response of the human eye in a particular part of the visible spectrum. This color change is independent of any change of hue with viewing direction through the crystal that would arise from pleochroism. Alexandrite results from small scale replacement of aluminium by chromium ions in the crystal structure, which causes intense absorption of light over a narrow range of wavelengths in the yellow region of the spectrum.

Alexandrite from the Ural Mountains in Russia is green by daylight and red by incandescent light. Other varieties of alexandrite may be yellowish or pink in daylight and a columbine or raspberry red by incandescent light.

According to a popular but controversial story, alexandrite was discovered by the Finnish mineralogist Nils Gustaf Nordenskiöld (1792–1866), and named alexandrite in honor of the future Tsar Alexander II of Russia. Nordenskiöld's initial discovery occurred as a result of an examination of a newly found mineral sample he had received from Perovskii, which he identified as emerald at first. The first emerald mine had been opened in 1831.

Alexandrite 5 carats (1,000 mg) and larger were traditionally thought to be found only in the Ural Mountains, but have since been found in larger sizes in Brazil. Other deposits are located in India (Andhra Pradesh), Madagascar, and Sri Lanka. Alexandrite in sizes over three carats are very rare.

Some gemstones described as lab-grown (synthetic) alexandrite are actually corundum laced with trace elements or color-change spinel and are not actually chrysoberyl. As a result, they would be more accurately described as simulated alexandrite rather than synthetic, but are often called Czochralski alexandrite after the process that grows the crystals.

"Look, here it is, the prophetic Russian stone! O crafty Siberian. It was always green as hope and only toward evening was it suffused with blood. It was that way from the beginning of the world, but it concealed itself for a long time, lay hidden in the earth, and permitted itself to be found only on the day when Tsar Alexander was declared of age, when a great sorcerer had come to Siberia to find the stone, a magician."       Leskov Nikolai Semyonovich. Alexandrite. 1884