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Alexandrite

alexandrit_2Alexandrite is one of the most beautiful and perfect gemstones born in the depths of Russian soil. This unique mineral is able to change its color depending on the light. This property is called reversion, and the term itself is used only in Russia. The cause of reversion is small inclusions of chrome. Alexandrite is a variety of chrysoberyl (beryllium and aluminum oxide BeAl2O4).

Alexandrite was first discovered in 1834 by N. Nordenshild, a mineralogist working in the emerald mines. When he found the crystal, Nordenshild first thought it was an emerald, but then he found out its hardness was higher – 8.5 instead of 7.5. Only in the evening did the mineralogist understand that he had found a new gemstone, previously unknown. In the light of a candle, he found that the stone, which was deep-green in the daytime, suddenly changed its color to reddish-purple! However, there is a variety of alexandrite that does not change color. Before, reversion was attributed to emeralds, but such stones did not contain any chrome that was responsible for reversing the color in their crystal, so there was no color-changing effect.

By pure chance, the first alexandrite was found on the 17th of April, when the future emperor Alexander II came of age. So the new finding was named after the tsar. But the unique ability of the stone to change its color turned out to be a death knell for the “god-child.”

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Upon ascending to the throne, Alexander II began the long-awaited reforms, including abolishing serfdom, a deed that earned him the name of The Liberator. But a terrorist’s bomb ended his life. In memoriam of the monarch who passed away so prematurely, many people in Russia started to wear alexandrite jewelry. It was considered to be the symbol of loyalty to the throne and compassion towards the victims of the revolutionary terror, but at the same time, it said a lot about the owner’s fortune and social position. Even in those times, it was quite difficult to buy an alexandrite ring. According to Leskov, “there were people who made quite an effort to find an alexandrite, and more often, they failed than succeeded.”

In Russia, the most well-known example of alexandrite is the druse that was found in 1840 in the Urals and is now preserved in the Fersman Mineralogical Museum. The “Druse of Kochubei,” a 22x13 cm stone with fantastic crystals, where the biggest one (6x6 cm) is dark-green in color. Unfortunately, all of them are virtually non-transparent. Another druse of almost the same size was found in 2001 during the analysis of the ore waste in the “Emerald Mines” warehouse in the Urals.  In the Museum of the Mining Institute in St. Petersburg, there are preserved, transparent crystals of alexandrite (6x3 cm) from the Urals’ mines. But the largest cut alexandrite, weighing 66 carats (13.2 g), belongs to the Smithsonian Institute in Washington, D.C.

Nowadays, alexandrite can be found anywhere in the world. But the only deposit where solely alexandrites--and in large quantities--were found was situated in the Urals. The past tense here is used intentionally; the deposit has been depleted long ago due to ill-conceived gophering. Now, alexandrite is mined along with other stones. In Russia, it was also found along with emeralds in the Malyshev mines described above.

Alexandrite in the rockAlexandrite in the rock alexandrit_04 alexandrit_08

In Soviet times, the value of alexandrite was forgotten. In the 1960s it was not mined; only samples were gathered. After that, the deposit was used for military purposes only, and beryl was mined. Kozlov, one of the geologists working in the mine, gave the Academy of Science a whole collection of alexandrites and was subsequently granted an apartment. When the 1990s came, the borders opened and the price of alexandrite soared. Some lucky geologists suddenly understood that a funny-looking sample on their shelves was, in fact, a stone of a very high value. One could buy an apartment in Moscow for a handful of good stones, let alone a whole collection.

In the daylight, the color of the Ural alexandrites varies from blue-green to yellowish-green, and in electric light, they change from gray-brown and gray-pink to purple and reddish-violet. A transition from the deep-green (or bottle-green color, as the gemologists say) to the saturated red is considered the best. As for lower-quality stones, the red color descends to brown, while green gets discolored and becomes blue. The high level of color gradation when the source of light changes is very common in Russian stones. That is why they are so valued on the international market. But the problem is that there is a lack of large and clear crystals among alexandrites. Most of them, even those rather small-sized ones, contain clearly visible inclusions. The optimum size of an alexandrite is two carats. Larger stones show a considerably weaker reversing effect while the number of cracks grows drastically.

Sri Lanka, where the largest known crystal weighing 1.876 carats was found, as well as Zimbabwe and Kenya, are the main suppliers of alexandrite on the market today. In addition, the deposits in Myanmar, Madagascar, Tanzania, and the U.S. are also well known. In 1987, a deposit was discovered in Brazil. It is interesting to know that in Brazil, Madagascar, and Russia, emerald and alexandrite embed together, while in Sri Lanka and Tanzania they are embedded separately.

In Sri Lanka, some occasional alexandrites with the cat's eye effect are found. Such crystals are very valuable and their price is comparable to the best Russian alexandrites. But keep the following in mind: in Sri Lanka, there are lots of crooks who will call a stone an alexandrite, but it will really be a local garnet, a stone that has a similar color reversion effect, but with a market price that is considerably lower.

alexandrit_05 Geologists who do not care a bit about marketing call the ‘color of green bottle’Geologists who do not care a bit about marketing call the ‘color of green bottle’ alexandrit_09

Brazilian and African stones are brownish-green in the daylight. In general, they are not as attractive, and their color is not even near that of emeralds, unlike the Ural alexandrites. But in the electric light, the “foreigners” look a lot more spectacular. They are usually redder than our stones, but also bigger and clearer. Stones from the Brazilian deposit of Hematita have a sharp contrast in gradation from crimson red to bluish-green.

Don’t take what is said about the “large” alexandrites literally, even when it comes to foreign crystals; average weight of this stone rarely exceeds 15 carats. Russian gemologists call the stone of larger sizes “SHURIC”; their color is rarely beautiful, and their reversion is rather poor.

The most popular cut for an alexandrite is the trap cut, or the brilliant drop cut. Despite its hardness, the stone lends itself to cutting by an ordinary silicone carbide emery wheel, though some prefer the copper diamond wheel. The cutting is done in the usual way: sometimes small crystals are polished with the alumina on tin. Cabochons are polished on the wooden or plastic wheels (spools). While polishing, the cutter should use a lot of physical force, but one should not fear the cracking that is caused by the high temperatures.

Sometimes, another variety of color-changing stone, andaluzite, can be confused with alexandrite. But actually, andaluzite is even rarer. The biggest problem for alexandrite is the synthetic stones. It is relatively easy to grow the alexes “in vitro.” But more often, the synthetic corundum and spinel are used to imitate alexandrite. Due to different admixtures, like vanadium, it is possible to reproduce the alexandrite-like reversion in the synthetic stones. Such stones often pass for alexandrites, though, in fact, they are nothing but an imitation and cost many times less. Moreover, it is a pure and simple imitation, not even a synthetic variety of the precious stone that has another type of the crystalloid structure.

In the former USSR such, “alexandrites” were used on a particularly large scale, when their industrial production started in 1973. The stones were grown in Novosibirsk, though not any longer. Customers were not informed even a little bit about the artificial nature of the stones, and they thought that they were buying jewelry with the real gems. But Russia is not the only country where the imitations are sold. The USA market has lots of artificial alexandrites that are sold under the guise of natural gems from Brazil, Sri Lanka, and Africa. It is likely that even the dealers do not know what they are actually selling, but in any case, the whole natural vs. artificial mess holds down the demand and, apparently, the prices for this stone.

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At the same time, it is quite easy to tell an “incubated” alexandrite from a natural one. You can protect yourself from a fake even without any special education or equipment. The first marks of suspicion are: first, the unusual clarity of the stone (total absence of inclusions), especially when the stone is big; second, the peculiarities of its coloring – blue-violet in the daylight and red-violet, almost amethyst one, in the electric light.  Any gemologist in any crudely equipped laboratory will easily tell an artificial “alex” from a natural one. It is hard to tell what will become of the price of a natural alexandrite when this mess is eventually sorted out.

The price of alexandrite is already quite high. With varying success, alexandrite and emerald struggle for the third position in the gemstones’ table of ranks. The price of a 10-15 carat cut stone may reach $20,000 to 30,000 per carat. A quality, one-carat gem costs from $5,000. In this case, it should not contain any visible inclusions and should have a good reversing. The best reversing is from bluish-green to purple-red. These days, the most expensive alexandrite on the market was sold at the Christie’s auction in 1990 for $205,333. It was an oval-cut stone weighing 28.32 carats. Generally speaking, carat-wise (7,250 USD per carat), the price was quite good, because smaller stones rarely cost less than $10,000 per carat.

Still, in spite of its interesting features, alexandrite is used quite rarely in the jewelry business. The inserts made of natural alexandrite in the jewelry pieces are extremely rare, as almost all cut stones go to the gemological collections. The rare items on our market are, as a rule, made abroad; for some strange reason, our Ural stones are treated only by the foreign jewelers. But if you are lucky enough to buy a piece with alexandrite, pay attention to the following when evaluating the stone:

  1. Color change--the rarest and most valuable stones change color from red-purple to bluish-green without any intermediate brown
  2. Intensity of color--the more, the better
  3. Clarity--absence of inclusions
  4. Quality of cut

As a rule, an alexandrite is set into the piece surrounded by small brilliants to help the stone to better showcase its color play. The shine of the brilliants should not overshadow the alexandrite but rather highlight its unique beauty.