Explanation Of a Color Change in Natural Alexandrites. Color Change Tutorial.
It is a paradox that what is considered an impurity is responsible for a color change phenomenon. The color change phenomenon is a result of the presence of chromium.
Thus the more chromium, the greater the color change. But unfortunately, a lot of chromium also makes the stone dark. Therefore clean, brilliant Alexandrite exhibiting visible color change is extremely rare and always fetch premium prices. Here is the quote from a reputable gemologist who is an expert on alexandrites:
"Alexandrite is a Type II (GIA Clarity Grading System) stone, and even the best Alexandrite is expected to contain many inclusions. The top quality alexandrite cost up to 100 thousand dollars per carat."
The following is from one of the most prominent GIA gemologists :
HOW TO VIEW THE ALEXANDRITE:
Contrary to the popular view, alexandrites usually display easily visible color change only in candlelight or low-watt yellow electric bulb(20-30 watt).
It should be green in sunlight and fluorescent light.
It should be purple in soft incandescent light. A low-lit or dark room is the best place to see the color change. Light from a candle will also show the purple color change. Very, very infrequently, an alexandrite will exhibit a change to a more reddish color- reddish-Violet, Violet-red, etc. These gems command a significant premium in price.
Mixed-light will produce either a grayer color as the green and purple mix or flashes of green, purple and sometimes red or yellow. Strong color-change stones will usually show the red/purple color in mixed lighting.
Rotate the stone to get the color from all facets and look for 'flash' (blazes of color that show in the body of the stone). Ruby-red flash and sparkle are the most desirable and most rare.
The more transparent is Alexandrite, the less saturated color change it usually displays.
It is essential to know that the cleaner is Alexandrite, the less noticeable change it usually displays. It is always the dilemma- we always have to choose either the color change or the clarity.
"An alexandrite with good clarity may display a less dramatic color change because the silky inclusions of rutile often enhance the change. Some people may prefer a weaker color change in favor of better clarity. However, the degree of color change is a most important factor defining the value of the Alexandrite."
Even the alexandrites with strong color change do not exhibit the second color on the street or in the room with standard lighting, but only in the darkroom near the candlelight or 30-watt yellow electric bulb.
This is how Alexandrite's color change was first discovered in Russia. There were no electric lights, only candles and fires. And Russian Royalty enjoyed observing the color change in the candle lights.
Here is the continuation of the guide on natural alexandrites:
"Although the optimal color change in an alexandrite would be from a brilliant emerald-like green to a ruby-like blood red, gemological experts agree that contrary to what many people believe, there are very few alexandrites which change color to a ruby red.
There is a wide range of lovely colors to be seen in these amazing stones. The few that do change from deep green to burgundy are often dark in tone, opaque, or highly included, so that many consider them unattractive.
So don't automatically assume you are getting a lower quality alexandrite if the color change doesn't go to ruby red.
By the light of a candle or flame, most alexandrites will exhibit reddish tones, but not under today's bright or "soft white" household bulbs!
Even fine alexandrites require more than nuances in lighting conditions in order to change color. They will normally show shades of bluish-violet by the light of regular incandescent bulbs or in the shade while remaining mostly green under mixed incandescent and sunlight or incandescent and fluorescent lighting.
Furthermore, if the light source is too bright, whether incandescent or not, some green will almost always be present. Also, it is scientifically proven that some people's eyes see the color change differently from others. It's true! It has been observed that an alexandrite may not exhibit the same colors and color changes in one geographical region that it does in another, perhaps altitude and climate change being a factor.
Whatever the case, it is only by candlelight or firelight that the most dramatic color change from green to reddish-purple will be seen.
What you should look for in a quality natural mined alexandrite is a shade of teal, emerald, or forest green under natural daylight or fluorescent lighting, ideally changing to a soft amethyst purple under regular incandescent bulbs, but more often a slightly grayish, bluish violet is seen, again more closely resembling tanzanite or a purple sapphire than a ruby. The color will usually deepen to plum by very low incandescent light.
Of one thing you can be sure - every Alexandrite is an individual, and it is rare to find two that display precisely the same colors under a variety of lighting conditions. This characteristic of individualism is due to a combination of factors, including variances in clarity and color, as well as the shape and cutting of the stone. It makes Alexandrite all the more valuable and endearing to collectors.
Even though "seeing the purple" seems to be necessary to buyers, many of us experienced with alexandrites think the vivid, gorgeous emerald-like bluish-green of a fine alexandrite is the most beautiful shade! Always remember, green must be the dominant daytime color for the stone to be a natural alexandrite!
Do not expect natural alexandrites to exhibit the same brilliance as diamonds or simulated alexandrites. They have a different crystal structure and refractive index. Sometimes buyers have an opinion of what their "ideal" Alexandrite should look like, often from having seen only lab-created stones, which leads to disappointment when they see a natural stone. So above all, wear your natural Alexandrite with pride, knowing you can enjoy flaunting a rare gemstone that was once preferred and possessed by only a select few!"
In 95% of jewelry stores in the US, you can't even find gem-quality Natural Alexandrite, and in the remaining 5%, if you do find it, it will cost about three times more than what you would pay in our store.