In sunlight, the stone takes on a greenish tint; in artificial light, it becomes reddish or purple. Alexandrites from a deposit in the Urals are considered standard: on the world market they are called “Russian”.
Alexandrites are mined only in a few places on the planet, so jewelry-quality samples are highly valued. Fortunately, man has long learned to create precious stones no worse than natural ones. Synthetic alexandrites resemble the best Ural specimens: clean, bright, with a strongly pronounced reverse.
History of synthesis
Alexandrite is a type of the mineral chrysoberyl. The first attempts at its synthesis were made in the second half of the 19th century: the French chemist Jacques Joseph Ebelmain was able to obtain chrysoberyl crystals measuring 5-6 mm in size. He was the first to synthesize a mineral compound that has no analogues in nature, but with the optical properties of alexandrite.
To obtain synthetic chrysoberyl, Ebelman and his students calcined beryllium and aluminum oxides in the presence of mineralizers. The crystals turned out to be small, with numerous flux inclusions. They were not suitable for jewelry purposes.
In the mid-twentieth century, attempts were made in the USA to obtain synthetic alexandrite from a solution in a melt. At first the crystals were small, but by 1964 it was possible to develop a synthesis method suitable for use on an industrial scale. In 1972, the Americans K. Kline and D. Patterson filed a patent for the method of flux from a solution in a lithium molybdate melt.
In 1970, the Japanese company began producing synthetic alexandrites obtained by the Czochralski method - by drawing a crystal from a melt. They were called "kresent-vert" and "inamori". Alexandrites "inamori" had a cat's eye effect - a running glare on the surface.
Currently, alexandrites are synthesized using the zone melting method and the Czochralski method. The resulting crystals are used for both jewelry and technical purposes. Synthetic alexandrites of the best quality are obtained by the Czochralski method.
How to grow alexandrites
To obtain synthetic alexandrites, low-quality natural stones are used. The crushed raw materials are heated and melted. To obtain the desired color, vanadium and chromium oxides are introduced into the melt.
The synthesis process is carried out in a special container, or crucible. It must withstand high temperatures, so it is made of refractory metals - for example, iridium. This platinum group metal costs 3 times more than gold, which affects the final cost of synthetic alexandrites: they cannot be called cheap, although they are cheaper than their natural counterpart.
During the synthesis process, a seed of sapphire or other stone, mounted on a vertical rod, is placed in the melt. Then it gradually rises, rotating and turning, and “pulls” part of the melt behind it. This hardens to form an alexandrite crystal. The cycle is repeated several times until the melt is exhausted.
Stone price
Synthetic alexandrite is significantly inferior in cost to its natural counterpart, but this does not affect the quality of wear and appearance.
The price of a gem will depend on many factors, including:
- carat content of the mineral;
- main color;
- what the finished jewelry looks like, what metals and stones frame the jewelry;
- the origin of the mineral is synthetic or natural.
Alexandrite is a beautiful, rare and unusual gem. It can become the top of your collection. The choice of jewelry must be approached with the utmost seriousness, because stones are expensive. Purchase jewelry only from trusted, well-established jewelry companies. After all, they will be able to provide you with a certificate of authenticity, a small discount and a guarantee on the product.
Chemical properties
Alexandrite is not only a beautiful stone, but an extremely hard one. On the Mohs scale its hardness is 8.5. This means that the mineral is practically not scratched, and jewelry with it can be worn every day.
Synthetic alexandrite has the same hardness as natural alexandrite. Its edges do not wear off during wear and remain smooth and neat. And if jewelry with an expensive natural stone may be unsafe to wear every day, then with a synthetic one it is completely safe.
What to consider when buying a gem
The first thing you should pay attention to when purchasing products with alexandrite is the size of the stone. Large, richly colored gems at a very reasonable price will 100% turn out to be fake. A weight of 2-4 carats is the maximum size that modern jewelry brands can offer and such products will cost from several thousand to several tens of thousands of dollars, depending on the purity and natural color of the mineral. The price of even the simplest grayish-colored gems starts from $300-350.
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It doesn't hurt to know what natural alexandrite looks like. Saturated bright color is practically not characteristic of it. Bright green, reddish and purple gems are most likely to be imitation or synthetic. The original has a calm color and moderate transparency.
If there are air bubbles in the crystal, their shape should resemble a drop. Bubbles-spheres are a sign of a synthetic mineral.
Important! Most jewelry made in the 19th century has natural alexandrite inlays. However, before purchasing, it is still recommended to conduct a spectral analysis of the stones.
Comparison of characteristics
When evaluating alexandrite, the color, severity of the reverse, clarity, weight and quality of cut are taken into account. For example, low quality natural stones weighing 3-5 carats
cost on the world market from $600 per carat. Alexandrites of the same mass, but of excellent quality - from 17 thousand dollars per carat and above. Large stones are valued even higher: the record is about 70 thousand dollars per carat.
Synthetic alexandrites are graded for the same characteristics. They cost much less.
Color
In daylight, alexandrite displays a palette of shades ranging from yellow-green to green and bluish-green. Yellowness makes the stone cheaper. The most valuable are alexandrites, which turn green or bluish-green when exposed to natural light.
Under artificial light, the stone takes on a reddish color, sometimes with an orange or purple tint. Red color without additional shades is the most valuable.
Synthetic alexandrites have purer colors than natural ones. This is due to the absence of iron impurities in the crystal. In daylight they look green without a yellow tint, in evening light they look crimson. Some stones also exhibit a cat's eye effect.
The cost of natural alexandrite also depends on how pronounced the color change is. It can be strong, medium or weak. Synthetic alexandrites are characterized by a strong reverse: in this they are comparable to the best Ural specimens.
Purity
Most natural alexandrites have minor inclusions - single points, gas-liquid veils, microcracks. They are not always visible to the naked eye, but they reduce the cost of the stone.
Synthetic alexandrites obtained by the Czochralski method are very pure. They contain almost no inclusions.
RusGems alexandrites were grown precisely by the Czochralski method according to the principle of recrystallization
Weight
Natural alexandrites are usually small: stones weighing less than 2 carats are common on the world market. Larger specimens are found, but much less frequently.
The Czochralski method makes it possible to grow really large crystals - both for jewelry and for technical purposes. The weight of individual specimens reaches 0.5 kg or more.
Cut shape
For alexandrite, the shape and quality of the cut are important: it should emphasize the color and optical effects inherent in the stone. The most popular options:
- "oval";
- "circle";
- "pear".
Alexandrites with a cat's eye effect, as well as opaque stones, are treated with cabochons.
Alexandrites RusGems in different cuts
Natural stones often do not have an ideal cut: in order not to cut off too much material, the cutter deliberately deviates from the standard - for example, skips some of the faces, or changes their angles. This negatively affects the visual perception of alexandrite and reduces its value.
Synthetic stones have a standard cut. The master does not need to save on material, and therefore the proportions are precisely adjusted.
Historical facts
The stone was found during the reign of Alexander II. Lev Perovsky (mineralogist of that time) wanted to call the samples diaphanites. But the imperial age changed the name of the mineral; they became alexandrites. A precious mineral was named after the young king. The researcher who revealed to the world the beauty of earthly gifts is Nils Nordenskiöld. The scientist mistook the stone for an emerald.
The only difference was in the hardness of the rock; the color and shine were completely the same. The mineralogist took the find with him, deciding to conduct home research. Imagine his surprise when he discovered that the stone had turned red, not green. It is clear that this was a new type of precious mineral. He was sent to St. Petersburg for detailed study. The breed is no longer found in its pure original form today. Modern stone began to contain various impurities, it lost its transparency and nobility, and became cloudy.
Distinctive features of natural breeds:
- double refraction of rays;
- original colors: bright red, yellow, green;
- changes under ultraviolet light;
- turns red under fluorescent lighting;
- Daylight reveals shades of the green palette.
Alexandrite does not react to magnets, but sometimes it can be attracted to it, but this is if there are a lot of additional impurities in the rock. The gem is a type of chromium-containing mineral, chrysoberyl. The export of stones from the Russian Federation is prohibited if it is not cut or has a frame. The gem adorns antique products; more often it is part of family collections. You can get acquainted with them at exhibitions in museums and antique shops.
How to distinguish synthetic alexandrite from natural one
The differences between synthetic and natural alexandrite are noticeable under a microscope. Gemologists focus on the number and nature of inclusions. The easiest to recognize are stones synthesized by the Czochralski method - they are very pure. In addition, synthetic alexandrites exhibit stronger reversal and fluoresce red in ultraviolet.
Cat's eye stones produce a faint fluorescence - orange-red on the inside, and pale yellow on the surface. They are also distinguished using a microscope. Synthetic alexandrites are dominated by fine silty particles, while natural ones are dominated by tubular and needle-shaped inclusions.
Color range and varieties
There is probably no stone in the world that could compare with this gem in terms of its unique properties. Like all gemstones, alexandrite is an expensive mineral. If natural rubies and emeralds are rare, but can be found in regular sales, it is believed that jewelry with such a stone is an exclusive acquisition, which not everyone can afford to buy. Of course, if you managed to acquire alexandrite, the natural composition of which is beyond doubt among professional appraisers, this is a valuable catch.
For a professional appraiser, the main role in a stone is played by its color scheme. The shades of the mineral can vary from green-blue in daylight to bright purple in artificial light.
There is no consensus among jewelers about which color of alexandrite is the most valuable: everyone sees something different in this amazing stone. Some believe that the price is determined by the intensity of the red palette, while others prefer deep green tones. There are certain varieties of gems that look beautiful only during a certain daily period under individual lighting, which can be either natural or artificial. The colors of alexandrite are determined both by the structure of chromium ions and by the characteristics of the deposits where the stones are mined. Ural specimens rightfully received the status of minerals with the deepest color reverse from jewelers. Daylight allows you to see many of their shades: classic green, a rich palette of blue and soft purple.
When exposed to sunlight, minerals from Africa and Brazil begin to display a wonderful blue color with a clear greenish tint. If you shine a lamp on them, they turn purple, and look even brighter than Ural red alexandrite.
As for the emerald green shade of the stone, beloved by many, it is most pronounced in the Ural nuggets - in this regard, they are the brightest and most prominent.
How to distinguish synthetic alexandrite from imitation
There is a myth that in Soviet times a huge amount of jewelry with alexandrites was sold. Ural precious stones were used as inserts, and they cost mere pennies. Unfortunately, this is not so: the stones were not natural, not from the Urals, and not alexandrites.
In jewelry, several imitations with a color changing effect are used:
- synthetic corundums;
- synthetic spinel;
- doublets;
- cubic zirconias;
- nanotals.
Synthetic corundum is the most successful imitation. A crystal colored with vanadium turns pale green in daylight, and pink in artificial light. It can be recognized by its color palette, inclusions in the form of bubbles, as well as a narrow, clear line in the blue region of the spectrum.
Synthetic spinel was used to imitate alexandrites in the USSR. It is distinguished using a refractometer. Spinel is characterized by the absence of birefringence, a significantly lower refractive index, and a less diverse and plausible range.
Doublets are made from garnet and glass. The garnet top imitates the redness of alexandrite, while the glass top imitates the green. They differ from the original in hardness and other physical properties, and are also inferior in gloss.
Cubic zirconia has almost twice the density of alexandrite. In synthetic crystals, inclusions and growth lines will be noticeable under a microscope, but not in artificial cubic zirconia and nanotals.
Main conclusions
Natural alexandrite is extremely rare. Its market value is very high, so there are frequent cases of sales of counterfeits posing as this imperial stone.
- The main difference between alexandrite is its color reverse, depending on the nature of the lighting. It was this property that made it so attractive and in demand.
- The naturalness of the mineral is confirmed by its dispersibility, size, hardness, muted shade of the stone and a certificate with the results of gemological examination.
- Most often, synthetic analogs, lower-class natural gemstones enriched with impurities, and glass are used as replacements.
- In most cases, a cheap fake made from glass can be identified by eye, but if natural minerals were used to create it, you will need the help of a specialist.
There are not many products and accessories on the market with natural alexandrites, primarily due to their high cost. However, if we are talking about ancient jewelry with a centuries-old history, then most likely they use natural stones. And yet, even in this case, it is worth conducting additional examination.
Is synthetic alexandrite better or worse than the original?
The main advantage of synthetic alexandrite over natural alexandrite is price. Although due to the high cost of production it cannot be called completely cheap, it is still much cheaper than the original. Visually, the stone is indistinguishable: to see the differences, you need a microscope.
Alexandrite synthesized by the Czochralski method has pure and bright colors. It exhibits a strong reversal: it turns from red to green when the lighting changes, and vice versa. Natural stones with such a pronounced color change effect are rare.
Synthetic alexandrite is practical. If you love this amazing stone, you can wear jewelry with it every day without worrying too much about possible loss. Jewelry with natural alexandrites, which cost fabulous amounts of money, will most likely remain in the box most of the time.
origin of name
The crystal was named in honor of Tsarevich Alexander Nikolaevich (the future Emperor of All Russia Alexander II), who celebrated his 16th birthday on the day when the unusual mineral was transferred to Nordenskiöld. Thanks to this, the stone became associated with imperial power and luxury.
Later, during the First World War, it was called the widow's stone. This name was assigned to alexandrite due to the fact that many ladies from high society lost their husbands, fathers and sons on the battlefields.
Since most rich women had such jewelry, a superstition arose among the people that the stone brings misfortune and leaves its owners without a partner.
