June 14, 2021
On the photo: 5-ct alexandrite from Sri Lanka under different lighting
Alexandrite is a precious stone known for only less than two centuries. It was firstly found in 1830 in Russia, in the Urals. It is a type of chrysoberyl mineral. The name of the stone was given on the occasion of the coming age of the Tsar of Russia Alexander II. Alexandrites were very popular in the late 19th century in the highest circles of Russian society. Together with rubies, sapphires, emeralds, diamonds, they are referred to as a special “top” category of the rarest and most expensive gemstones in the world.
Why are alexandrites so valued? There is a very little quantity of gem-quality alexandrites on the world market, much less than rubies, sapphires or emeralds. Let’s consider the factors that influenced of beauty and value. Rarity is one of them. At the present time it is quite problematic to find a natural specimen of good quality for more than 2 carats in sale. The main problem is to find alexandrite with attractive colors.
Natural alexandrites, in addition to their rarity, have become especially famous for their unique colorchange optical phenomenon - they change color depending on the type of lighting. This effect is known as the «Alexandrite effect». In daylight (white light), alexandrites demonstrate bluish and greenish hues, and in candescent light (yellow), they change to shades of red, pink or purple. Stones with strong colorchange effect are the most valuable and are extremely rare. Alexandrite is also characterized by strong pleochroism, when different tones can be observed at different angles in the stone. For example, red, yellowish orange and green.
The color of alexandrite is the main factor affecting the perception of its beauty. In daylight, the most valuable colors are green and bluish-green. The yellowish-green color of alexandrite is considered less valuable. The most expensive color in candescent light is red without additional shades. In addition, alexandrites can show red with a violet or orangish shade. Alexandrites with violetish shade come from Brazil and Tanzania. You should keep in mind, that particularly all alexandrites with strong colorchange effect are dark. Saturated colors could be seen just in bright lighting, for instance, in the direct “white” or “yellow” light of torch. If we don’t shine a torch on it, we observe unimpressive color, for example, brown with insignificant shades of pink or green. A stone, that changes color from bright green to bright red (but not violet) is a myth, not reality.
On the left photo: different colors in the sample from Tanzania weighted 5.19 ct
To find faceted alexandrite with attractive color is very tough task. Just a very small part of mined samples in natural light shows good color. Colors of stones on photos are usually edited in graphic redactor. So you shouldn’t believe to colorfully photos in books or internet resources. During taking photos, the color is often misrepresented and we may see unreal shades of green or red. Alexandrites usually look very beautiful on photos, but it does’t mean that photos demonstrate real color, and in life stones could distinguish from photos.
On the right photo: an alexandrite sample 6.18 ct under gemological lamp (top) and under “yellow” light of flashlight (bottom)
“Practical advice for purchase alexandrite. Firstly, look at the color in different types of lighting. The most important thing in this case is that you should like the observed colors. While the stone is in the tweezers or in the hands, looking at it from the side of the site. Balance the stone in tweezers, looking at it «face up». Judge its color and colorchange effect in different lamps, near a window or outdoors and in incandescent light. You can use torches with «white» and «yellow» light. Note for yourself, whether the stone light or dark, judge saturation (color’s intensity), color distribution in the stone and additional shades. You can also shine on it with two different light types simultaneously. Beauty of the stone significantly depends on its color. “
The second qualiry factor is alexandrite clarity. This precious stone belongs to the type of clarity with not large quantity of cracks and inclusions. It is characterized with fingerprints inclusions. Absolutely clear samples without internal defects are extremely rare. Opaque alexandrites goes on cabochon making.
On the video: dark alexandrite, with invisible inclusions 10.23 ct, origin – Sri Lanka
“ Practical advice. After color evaluation, evaluate its clarity. Make sure that the sample is well wiped and has no dust on the facets. Firstly, check the clarity with the naked eye. Are cracks of inclusions well visible? It is desirable that they are not in the center of the faceted stone. Look, how much defects influence on the overall attractiveness? Then, you can notice transparency Then, look at the transparency of alexandrite in a 10-fold gemological loop for a more comprehensive analysis. At the same time, pay attention to whether there are any significant cracks in the sample that come to its surface. Their presence can affect the durability.“
The third factor is carat weight of alexandrite. Cost per carat of alexandrite will increase with weight increase. The rarity factor works here: the stones of considerable size are significantly rarer than small. Mainly in the world market alexandrite samples weighing less than 2 ct are presented. Alexandrite gemstones over 5 carats comes usually from Sri Lanka.
“Practical advice. You can roughly estimate how faceted alexandrite will look like being fixed in jewelry. To do this, put a stone between your fingers. Move your palm in different lighting and appreciate the whole appearance of alexandrite. Do you like it or not? In the same way, putting several samples on your fingers at the same time, you can compare them to choose the best one.“
On the video: large natural alexandrite with good clarity, 14.77 ct
– At the second part of the article we will consider such factors as cutting, deposits, fact of treatment, variety and certificate, that also affected price. At the third part of the article we will show you real prices per carat.
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