Jewelry with artificial and natural Alexandrite

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.

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.

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.

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.

Where is stone mined and processed?

Main places of mineral extraction:

• Russia;
• Brazil;
• India;
• Tanzania;
• Sri Lanka;
• Burma;
• Zimbabwe.

Alexandrite of the Urals is recognized as the gem with the most beautiful color scheme. Under artificial light, it turns violet or purple. Stones from Brazil are distinguished by smooth transitions between colors. Indian alexandrites have a bluish-green glow.

After extraction, the stones are washed with water, cut, ground, and polished. The main types of cuts are diamond and cabochon. Faceted gems lose weight, but gain in price.

Pale, untreated specimens can be irradiated with X-rays to brighten the mineral. Other refining treatments are not applied to alexandrite.

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.

1. 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.
2. 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.
3. Most often, synthetic analogs, lower-class natural gemstones enriched with impurities, and glass are used as replacements.
4. 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.

Artificial origin is not always a minus

Science and technology have brought the process of growing crystals to perfection: the physical, chemical and aesthetic characteristics of the imitation and the original are identical. It is impossible to reliably distinguish artificial alexandrite from natural one: this requires special equipment.

Synthetically created gems do not have a “widow’s stone” trail; such alexandrite products are suitable for all zodiac signs.

Artificial material is stronger, easier to maintain, and cheaper than natural material. Quite organic for the digital era.