Interesting facts about Alexandrite

Interesting facts about Alexandrite

                                                                                           
Alexandrite changes color from green in daylight to red in incandescent light. The first time you see it, it is hard to believe your eyes!  Alexandrite was first discovered in Czarist Russia, in the Ural mountains, on April 3 1834, when several crystals were found in Tokovanya deposits.  The name “Alexandrite” was coined by mineralogist Dr. Nordenskjöld (Finnish by birth but he worked for the Russian Czar). Since the old Russian imperial colors were red and green it was named after Czar Alexandr II on the occasion of his coming of age in 1842.  Genuine Alexandrite is one of the world's rarest and most coveted Gemstones, it's so rare that most people have never even seen a genuine Top Quality Alexandrite.

Alexandrite is in the Chrysoberyl mineral family and is one of the most fascinating gemstones throughout history. Alexandrite is the variety of Chrysoberyl that displays a change-of-color from green to red. A distinct color change is the primary qualification for a Chrysoberyl to be considered alexandrite. Although alexandrite is strongly trichroic, its color change has nothing to do with pleochroism. Instead, like all other color-change gems, it results in a near-equal transmission of the blue-green and red portions of the spectrum, coupled with strong absorption in the yellow. Thus its color is dependant on the spectral strength of the light source. Incandescent light is strongly tilted to the red end, thus causing alexandrite to appear reddish. Daylight, is more equally balanced. Since our eyes are most sensitive to green light, the balance is tipped to the green side. The strength of the color change is related to the difference in the areas of transmission, relative to the absorption in the yellow. The greater the difference, the stronger the color change.  The color is actually caused by Chromium.

A color change occurs in very few gemstones. For alexandrite, the quality of the color change is paramount. While the holy grail is a gem whose color changes like a traffic light from green to red, such a stone has yet to be found. In fine examples, the change is typically one from a slightly bluish green to a purplish red. The quality of color change is often referred to by dealers in a percentage basis, with 100% change being the ideal. Stones that display a change of 30% or less are of marginal interest and are arguably not even alexandrite. Significant brown or gray components in either of the twin colors will lower value dramatically.

The natural color change in Alexandrite ranges from various shades of Green (blue-greens, kelly-greens, olive-greens, teal-greens, etc.) when the gem is under "fluorescent" lighting, or in natural outdoor light "in the shade" (not direct sunlight)... then the color changes to various shades of Red (burgundy-reds, purplish-reds, reddish-purples, violetish-purples, amethyst, etc.) when exposed to light in a room with only incandescent light, tungsten light, or candlelight (a flashlight will bring out the color change too).

To get the maximum color change effect the gem is best viewed in a dark room with no outdoor light at all, then turn on a fluorescent light to see the green shade, then turn on a standard incandescent light bulb with the fluorescent light off to see the reddish shade.  You can cycle the lights back and forth to see the distinct color change.  Alexandrite will normally darken when taken out into direct sunlight, since it is subjected all the colors in the spectrum,  also if subjected to several types of lighting sources at the same time the colors may twinkle with both the red and the green color bouncing around different facets in the stone.  When the primary color has a bit of brownish in with the green, this is due to the bleeding of the two colors.  Typically this is referred to as the percentage of color change.  The higher the color change percentage, the more expensive the gem.