Chemical composition of Alexandrite
From a strictly mineralogical point of view, the Alexandrite is a chrysoberyl which belongs to the class of oxides and hydroxides, of which it represents the most coveted variety due to its ability to change color. This peculiarity is due to two factors: the quality of the light source and the way in which light is absorbed and reflected by the chrome. Natural light and artificial light have different amounts of spectrum colors (blue, green, orange, red, violet and yellow). The chrome absorbs the yellow while the white light passes through the Alexandrite and unfolds in equal parts of blue and green. The light of the sun, being more balanced and containing more of the preferred green to our vision makes Alexandrite appear in a blue-green hue; instead, the incandescent light (which has redder) shows us a color that tends to red and purple.
Extraction of the Alexandrite
The Russian Alexandrite is certainly the most celebrated, but it is no longer available in the gem market. Sri Lanka has long been along with Russia, the main source of Alexandrite extraction. Wonderful specimens have also been found in India, Tanzania, and Brazil. In lesser quantity, Alexandrite has been discovered in Burma, Madagascar, Mozambique, and Zimbabwe.
History of the Alexandrite
Extremely rare, the Alexandrite was discovered in the middle of the nineteenth century and immediately became the backbone of the Russian jewelry industry. Unfortunately, the source of original extraction has been exhausted and the only link with its land of origin has it through its name.
Characteristics of the Alexandrite
Together with the color change, which we have discussed above, the Alexandrite shows an excellent trichroism thanks to which this gem is able to show three different colors: green, red and yellow, according to the angle of observation. It is a type II precious stone, that is to say, that it has visible inclusions, especially in the examples that surpass the karat. Such inclusions in quality gems do not interfere with their beauty.
Varieties of Alexandrite
A rare variety is the Alexandrite cat’s eye, which thanks to subtle inclusions of retiling in the form of needles, reflects the light producing a similar effect to the pupil of a cat. This effect is known in the world of gemology as chatoyancy and is obtained with a stem and polished cabochon (a convex surface).
Care of the Alexandrite
The Alexandrite can be subjected to a steam cleaning treatment, but not to ultrasound treatment.