Imitation(lat. imitatio) is an imitation of someone or something; fake. Like everything rare, expensive and beautiful, precious stones have caused numerous attempts to reproduce them artificially since ancient times. Pliny had already written about glass imitations of various precious stones, as well as about the manufacture of triplets. In 1758, the Austrian inventor, chemist Josef Strass, mixing and fusing green flint, iron oxide, alumina, lime and soda, obtained a colorless mass, which it turned out to be possible to cut and grind, after which it began to sparkle like real diamonds. The basis of many fake stones today is a pure, unpainted glass alloy, named after Joseph Strass - rhinestone. It is widely used for imitation of precious stones and bottle and window glass, optical crown glass (alkaline lime glass), optical flint glass, and borosilicate glass. Manganese, nickel, copper, iron, chromium, etc. are used as dyes. Another imitation method is duplication, resulting in doublets and triplets. There are other types of fakes or imitations as well. For example, you can imitate natural opal by heating the glass and then quickly cooling it (Pliny wrote about this), as a result of which it becomes covered with cracks. Imitate natural gemstones, synthetic stones and various artificial products.

Fake stones- artificial production of stones imitating natural minerals - precious, semi-precious and semi-precious stones. These are synthetic stones, imitation stones. Many gemstones are based on a beautiful, clean, unpainted glass alloy (see rhinestone). They can be cut and polished, after which they acquire the ability to sparkle, like natural minerals. Another way to counterfeit is duplication. It consists in the fact that the upper (front) part, made of a real gemstone, is glued onto the lower (back) part, consisting of glass, rock crystal or synthetic material.

Here are the main ways to simulate:

Doublets- imitation of precious stones, obtained from two components. They were known even in ancient Rome. Today, doublets are made using opal: a thin layer of opal is glued to the opal uterus. Also used are sapphire, ruby ​​and garnet doublets, when a thin plate of the corresponding stone is glued on top of glass or synthetic spinel. They are called: doublet sapphire-glass or sapphire-synthetic spinel, etc. The emerald is imitated by making it from colorless beryl: faceted beryl is cut in half and glued to a green intermediate spacer. A pale emerald with an intensely colored glue is also used.

Artificial resin- materials used as imitation amber, as well as in jewelry for clothes (buckles, buttons, etc. are made from them)

Ceramic masses- a material such as porcelain or pottery, with the help of which jewelers successfully imitate opaque precious stones, especially turquoise. In addition, fashionable jewelry is now made from faience, majolica, porcelain: brooches, pendants, bracelets, rings, as well as various sets and headsets.

Optical crown glass- alkaline lime glass used to imitate precious stones.

Optical flint glass- English crystal, glass containing lead; used to imitate precious stones.

Semi-doublets- imitation of large gemstones, glued together from two of the same smaller stones. Since the value of precious stones increases in proportion to the square of their mass, such an imitation, issued for one large stone, will cost much more than both of its smaller stones.

Resol- a synthetic thermosetting polymer, which is a viscous liquid or a solid, soluble and low-melting product from light yellow to black. It is used to imitate amber.

Reinkisel(Rhine flint) - glass containing multicolored blotches (schlieren) in a white or colorless glass mass. Currently used as imitation material in costume jewelry.

Ruby doublets- imitation of natural ruby ​​by gluing a thin strip of ruby ​​stone on glass or synthetic spinel.

Sapphire doublets- imitation of natural sapphires by gluing a thin sapphire plate onto glass or synthetic spinel. They are called respectively sapphire-glass or sapphire-synthetic spinel.

Resin- chemically complex substances produced by resin-producing trees and synthetically. A distinction is made between soft and hard resins. Hard resins are as hard as gypsum, some are slightly harder, others are slightly softer, but most of them are scratched with a knife. There are transparent and opaque ones. One type of hard resin - amber - is widely used for the production of various types of jewelry. Some resins are used to imitate amber. In the manufacture of bracelets and some other decorative items, Indian craftsmen use shellac, dyeing resin in yellow and other colors.

Titanium glass(flint glass) - glass in which lead oxide is replaced by titanium oxide. Used to simulate natural minerals.

Triplet- imitation of precious stones, consisting of thin layers of natural stone, which is glued between two pieces of rock crystal. For example, a quartz-opal-quartz triplet. Counterfeits for precious stones were already known in Ancient Egypt and Rome during the time of Pliny. Pliny wrote about the manufacture of triplets: “It is very difficult to distinguish real from counterfeit ones, since a method has been invented to falsify gems of a certain kind, using genuine stones for this. So, they learned to glue sardonyx from three different gems so skillfully that it is impossible to detect it, although its black, white and red red colors actually all belong to different stones. "

Faience(French faience, from the name of the Italian city Faenza - Faenza, where the faience was produced) - ceramics made of white-burning clay, covered with a colorless glaze with a white dense fine-grained shard that is not translucent in a thin layer. Brooches, pendants, earrings, bracelets, headsets are made of faience, most often painted with paints and covered with glaze, or decorated with moldings (molding). Faience is an excellent material for imitating natural turquoise.

Phenoplasts- plastics based on phenol-formaldehyde resins. Easily processed and painted in any color. In appearance, they can imitate (see Imitation) natural stones, including pearls, coral, prelamutr, glass and other materials. They are used for making beads, earrings, rings, brooches, bracelets and other inexpensive jewelry.

Flintglass(lead glass) is a material used to imitate precious stones. Consists of oxides of potassium or sodium, lead oxide. Lead glass of the following composition is sometimes used to imitate a diamond: 38.2% silica, 53.3% lead oxide, 7.8% potassium carbonate and a small amount of other substances. This composition gives very high refractive indices of light. Previously, this material was called rhinestone. Flint glass is used to make cheap glass jewelry. Flint glass stones are beautiful when skillfully cut. The addition of lead increases light refraction and dispersion. But these imitations are soft, and therefore, in the process of wearing, during friction, they quickly lose their polish, scratch, and suffer from sulfur oxides present in the atmosphere. Over time, the jewelry takes on a brownish tint.

Phosphor glass- glass, which contains the same components as in crown glass, but part of the silica is replaced by phosphorus oxide. Used to simulate precious stones.

Glass is a common and cheap substitute for gemstones. It most successfully imitates their external properties. Glass inserts have a bright shine, transparency, good uniform color.

The composition of glass used for imitation gems varies. So, a composition can contain:

Silicon oxide (38 to 65%);

Sodium and potassium oxides (10 to 20%);

Calcium oxide (no more than 5%);

Barium oxide (3 to 8%);

Lead oxide (14 to 40%).

The most "beautiful" is the imitation of glass gems, called "stras" or "rhinestones" by the name of the German jeweler Georges Strass, who at the end of the 19th century. proposed the following formulation: 38.2% silicon oxide, 53.0% lead oxide and 8.8% potash. In addition, small amounts of borax, glycerin and arsenic acid are added to this mixture. Strass's recipe is used to make imitation diamonds, with lead glass being shaped like a full-cut diamond.

To obtain an imitation of a ruby, 0.1% of cassia purple is added to the rhinestone charge, which provides a red color.

To obtain a blue color that mimics a sapphire, add 2.5% cobalt oxide. The emerald (green) color is imitated by adding 0.8% copper oxide and 0.02% chromium oxide to the rhinestone. Amethyst can be obtained in the same way. For this, 2.5% of cobalt oxide and a small amount (to the required tone) of manganese oxide are added to the charge. Currently, glass coloring technology allows you to simulate almost any color, tone and shade by selecting the appropriate dyes.

By adding insoluble substances (bone meal, cryolite, tin oxide), an opaque white, milky glass can be obtained, which serves as an imitation of base opal. It is possible to obtain a black rhinestone - marblite by introducing 3-5% manganese compounds with iron oxides. This rhinestone is a perfect imitation of black tourmaline (sherla).

Giving rhinestones the required shape is carried out in several ways. In some cases, this is casting followed by grinding and polishing, in others - stamping. Hollow glass beads are blown.

Large rhinestones can undergo a special artistic treatment called copper wheel faceting. In this case, you can apply a variety of patterns to rhinestones and even bas-relief and high-relief images. Blown beads can be decorated by irisation, that is, by applying the thinnest layers of metal oxides, which give the rainbow effect of the same kind that is obtained from stains of oil or oil on water. To enhance the optical properties, silver amalgam is often applied to the lower part of the rhinestone, followed by its fixing by bronzing.

Rhinestones are easy to distinguish from natural gems, since they do not have a crystalline structure, are fragile, and their hardness on the Mohs scale does not exceed 6. or synthetic stone, it remains intact. Rhinestones differ from natural stones in their lower thermal conductivity, so the traces of breath disappear from glass more slowly than from natural crystals. Natural stones feel colder to the touch than glass imitations.

Currently, rhinestones are used mainly in the manufacture of jewelry of various levels of performance and cost.

In addition to rhinestones, there are other glass imitations. For example, the most attractive imitation of pearls is considered to be the so-called "Roman pearls", which are hollow glass beads, covered from the inside with pearl essence and filled with wax to give them an external impression of hardness. To imitate turquoise, they can use tinted frosted barium glass, as well as ceramic materials such as porcelain and earthenware. A fairly large number of glass opal imitations are known on the market.

Sometimes glass imitations may have incorrect trade names. For example, glass imitation tanzanite is known in the market as "synthetic tanzanite".

Imitation gems, namely synthetic stones are becoming more popular these days. Due to the fact that natural gemstones are expensive and very rare, there will always be imitation market and cheap imitations. In general, the purpose of imitations is to deceive people. They are made from natural and synthetic materials that look like real, expensive gemstones.

Imitations have been around for 6,000 years. Thus, the Egyptians used blue faience (glazed) to imitate turquoise. The Romans passed off colored glasses for emeralds and rubies. During Queen Victoria's time, a variety of materials were used to simulate mineral gemstones, including glass and resins.

Glass for imitation stones

Glass is the most suitable material because it can be painted in almost any color and cut, giving it the appearance of a real gemstone. However, there is a significant difference between glass and gemstones. As a rule, glass is much softer than the gemstone for which it is issued, and therefore, it is much easier to scratch.

There may be bubbles and funnels in the glass, which are easy to spot with a magnifying glass. A gemologist can easily distinguish glass by its single refractive index (1.5-1.7), because precious stones with a single refractive index equal to this value do not exist.

Imitation diamonds

One natural gem can be used to mimic another, more expensive, gem. For example, citrine can be used to simulate topaz, and non-colored quartz or glass can be used to simulate the diamond itself. Colorless glass cannot be considered a good imitation of diamonds, because it is not hard enough and lacks glow and shine.

Others imitation diamonds are cubic zirconia (cubic zirconia) and appeared relatively recently. It is about the same hard as diamond, on the Mohs scale its hardness is more than 9. The main difference is that diamond has one refractive index, while moissanite has two. In the larger crystals of moissanite this appears as a doubling of the pavilion's facets when viewed through the stone, but small moissanite stones embedded in jewelry are difficult to distinguish.

Other imitations of diamonds are also known, including yttrium aluminum garnet and strontium titanate, but all of them either do not have sparkle (spinel, topaz) or, on the contrary, sparkle too brightly (strontium titanate, rutile), or are very soft or too fragile. Imitations can be distinguished from diamonds due to the fact that they conduct heat much worse. Checking a stone with a device that measures thermal conductivity will immediately lead the gemologist to the idea of ​​a fake.

Composite stones: doublets with garnet top layer and glued emeralds. As imitation stones so-called composite doublets also appear. This method began to be used several centuries ago and became widespread in the 19th century. The gemstone layer is glued onto a solid base. However, most often ordinary glass is taken as a basis, which is coated with quartz or another not very expensive mineral.

For example, a piece of green glass with a thin layer of red garnet on top can be used as a fake emerald or green garnet. The garnet top doublet is in two parts, which can be easily installed due to the difference in gloss. In addition, the glass may contain bubbles characteristic of it, which are not in the pomegranate.

If you look at this "stone" from the upper platform, it appears green, but if you look at it from the side or submerge it in water, a red layer of garnet becomes noticeable. By changing the color of the lower, glass, layer, you can make imitation gems all colors. Another composite is a glued emerald made of two layers of colorless quartz, between which a thin layer of gelatin or green glass is enclosed.

Composite stones: opal doublets and triplets. A special category of composite stones includes opal doublets and triplets - thin "sandwiches" in which noble opal is present in the form of the thinnest layer. Opal doublets (they consist of two layers) are made by gluing a piece of noble opal, showing a play of color, with a substrate of base opal, quartz, chalcedony, glass or plastic. In addition to the substrate, opal triplets also have an upper, protective layer of.

Imitation opals

The play of color that noble opals are distinguished by is the result of light interference on the inner spherical structure of the mineral. In 1974, the French scientist Pierre Gilsson first demonstrated the obtained in the laboratory. Gilson's opals can be distinguished from natural stones by their mottling and mosaic-like “bundles” between the colored grains. American scientist John Slocum synthesized a glass opal known as the "Slocum stone". Under the microscope, the color spots in the Slocum stones appear somewhat wrinkled.

Glass is the cheapest and most common substitute for precious stones. At the end of the 18th century. Straße proposed a recipe for a special lead glass that successfully replaces precious stones: 38.2% silica, lead oxide 53.0% and potash 8.8%. In addition, borax, glycerin and arsenous acid were added to the mixture. This alloy is called rhinestone. It is characterized by high dispersion, and it lends itself well to cutting. This glass-lo was used to imitate diamonds. Later they learned how to make colored rhinestones. To obtain a ruby ​​color, 0.1% of cassian porphyry was added to the glass mass, 2.5% of cobalt oxide was added to sapphire, 0.8% of copper oxide and 0.02% of chromium oxide were emerald. Recipes were developed for obtaining imitations of pomegranates, amethysts, spinels.

Currently, glasses imitating precious stones are widely used in jewelry.

So, the chemical composition and physical properties of synthetic and corresponding natural stones are the same. However, synthetic stones are a product of human labor, and you can make them as much as you want.

Natural stones are the creations of nature, their number is limited, it is difficult to find and get it. That is why a gem is tens, and sometimes hundreds of times more expensive than its synthetic counterparts, despite the fact that synthetic stones are often significantly superior in quality and color characteristics to natural stones.

Jewelry stones are a wonderful creation of nature and man. Nature did not stint, creating a deep serenity of luscious green emeralds, the serenity of blue sapphires, the ardor of red rubies, the magical or passionate variability of white and black opals, the tenderness of pink and blue topaz, an endless sea of ​​flowers, shades, patterns. A person, having breathed his soul into them, carefully, with love, processed them, gave them completeness, completeness, turned them into real works of art, designed to bring people joy, pleasure, inspiration, and not grief and tears, not to be an object of profit and enrichment, but a testament to the wealth and enormous spiritual power of the people.

Glass used as imitation can be of different transparency (transparent, translucent, translucent in thin chips, opaque) and colors. Their physical properties depend on the composition, mainly on the lead content. Refractive indices of transparent glasses 1.44 - 1.77; hardness 5 - 7 on the Mohs scale; density 2 - 4.5 g / cm 3.

Glasses are isotropic, but over time they can develop optical anisotropy. Dispersion 0.010, in glasses with a high lead content can be higher.

Glasses can be distinguished by the presence of gas bubbles of various shapes, sometimes streaks, blobs of dyes. In addition to purely glass imitations, double (doublets) and triplets (triplets) stones are used, glued from glass and natural stone, from weak and densely colored stones, from natural and synthetic stone. Such fakes are perfectly visible under a magnifying glass or a microscope: on the gluing surface, bubbles are observed located in the same plane.

Glasses (and plastics) are used to imitate translucent and opaque stones: turquoise, chrysoprase, carnelian, etc. Their density and hardness are low.

Aventurine glass differs from aventurine in physical properties, as well as in the presence of a regular three- or hexagonal shape of inclusions of copper shavings.

Artificial or synthetic gemstones can be divided into four types:

• synthetic stones, i.e. artificial gems obtained by the synthesis of metal oxides;
• cultured pearls;
• natural imitations of precious and semi-precious stones;
• artificially colored and refined stones

Glass and plastic imitation of jewelry stones are also widely used.

The most famous synthetic gemstone is diamond, which is a modification of carbon. For the first time, diamond was synthesized by E. Lundblat's group in Sweden in 1953 (at a pressure of 8 GPa and a temperature of more than 2500 ° C). In 1954, the group of G. Hall in the USA, and in 1960, the group of L.F. Vereshchagin, the USSR also carried out the synthesis of diamonds.

Synthetic quartz was first obtained (in the form of columnar crystals 0.5-0.8 mm in size) by W. Bruns in 1889 in England.

In 1900, G. Spezia (Italy) crystallized quartz in an autoclave up to 2 cm in size. Large quartz crystals weighing more than 2.5 kg were synthesized in 1955 in the USSR.

Currently, yttrium-aluminum garnets (YAG), spinels (ganite), and also (in 1976) artificial zirconium - cubic zirconia (dzhevalite, daimonsquai) (Zr 0.8 Ca 0.2 O 1.92) have been synthesized.

Synthetic stones are understood to mean artificially obtained crystalline or amorphous chemical compounds that are similar in composition and structure to natural ones or have an external similarity due to their physical properties. By synthesis, obtained ruby, spinels, emeralds, quartz , as well as independent chemical compounds (garnet, cubic zirconia).

Synthetic, artificial gems, possessing the properties of natural stones, successfully replace them in jewelry made of precious metals, but they are cheap compared to natural ones, and glass imitations are just cheap fakes.

Synthetic corundums and spinels have a wide variety of colors, and the stones get their trade name from the existing analogues in nature - rubies, sapphires, tourmalines, alexandrites, aquamarines, etc. magnesium. Depending on the specified color, dyes are added: for ruby ​​- chromium oxide, blue sapphire - oxides of iron and titanium, cornflower blue sapphire - oxides of iron, titanium, chromium, alexandrite - vanadium oxide, etc.

The prepared charge (seed) is poured in a continuous stream through a hydrogen-oxygen flame ("detonating gas" flame), the temperature of which is higher than 2000 ° C, onto a refractory rod. A melt cone is formed on the rod, which descends at a predetermined speed. Thus, a single crystal grows in the form of a cylindrical rod (boule).

For getting synthetic star corundum (rubies and sapphires) titanium oxide is added to the starting material. In the process of synthesis, a mixed crystal is formed; upon its subsequent heating below the melting point of aluminum oxide, it decomposes with the release of the finest acicular rutile crystals. The arrangement of the rutile crystals in synthetic corundum is the same as in natural star corundum. When cut in cabochon, a synthetic ruby ​​or sapphire has the same star-like effect as a natural one.

Synthetic corundums and spinels have excellent physical and chemical properties; have zero porosity, high transparency, strength even at high temperatures, resistance to common acids and most alkalis. Their density is 3.98 - 3.99, the hardness on the Mohs scale is 9.

Synthetic emerald are obtained by flux and hydrothermal methods. The growth of crystals in both cases occurs on a seed made of natural beryl. The crystal growth rate is 0.8 mm per day. In most cases, synthetic emeralds have a distinct color zoning.

Synthetic quartz It is grown hydrothermally, and solutions of hydroxides and carbonates of alkali metals - sodium or potassium - serve as solvents of natural raw materials. By means of dyes (metal oxides) or irradiation, quartz can be obtained from colorless to black, including the colors of all its natural crystalline varieties.

Garnet (Yttrium Aluminum Garnet) is an yttrium-aluminum oxide with a garnet structure. In its pure form, garnetite is colorless, density 4.54, hardness on the Mohs scale - 8.

Garnetite is obtained in special apparatuses at high temperatures in a deep vacuum by the method of "pulling" the crystal from the melt. Due to its properties, colorless garnetite is used as an imitation of diamond, and with the help of additives, garnetite is painted in various colors.

Cultured pearls... Cultured pearls, like natural pearls, are grown in the body of a mollusc under natural conditions. A mother-of-pearl ball serves as an embryo. It is enclosed in a piece of the mantle shell of a three-year-old mollusk that produces mother-of-pearl, thus obtaining a "pearl sack". This bag is placed in another sink, which is placed in a special reservoir. The embryo enveloping can last from 2 to 7 years. As the pearls grow, the shells are checked several times a year. Grown pearls are outwardly indistinguishable from natural ones, they have the correct given shape. The shell of artificial pearls corresponds to the natural chemical composition and has the same physical properties. Cultured pearls can be grown in large quantities, take on specific sizes and shapes, and be as beautiful as real pearls.

TO natural imitations Precious and semi-precious stones include stones obtained from waste of natural stones by gluing, pressing, alloying, as well as natural stones painted in a different color.

One of the types of imitation gems - doublets(doubles), glued stones. Waste (thin plates) - natural gems that cannot be cut on their own, are glued with less expensive minerals, similar in transparency and color, and processed together. The most common doublets of sapphires and emeralds. Rhinestone and colored glasses can serve as adhesives. The doublets, therefore, consist of an upper part, an expensive mineral, and a lower part, a cheap one. If you look at the stone from above, the gluing of the doublet is invisible, but if you look at it, turning it sideways, at a certain angle to the light source, you can see a reddish strip along the perimeter of the gluing or weak reddish reflections of the glued edge. Doublets have all the optical properties of a gem and, since the bottom of the stone does not wear out, they are durable in use.

Amber imitate pressing and fusion. Pressed amber - small grains and fragments of natural amber heated and pressed under pressure; they differ from natural amber by a large turbidity. The gloss is oily, and the hardness and chemical properties are within natural limits.

Fused (fused) amber is a low-melting mass obtained as a result of the decomposition of amber during dry sublimation at a temperature of 420 ° C. Color from yellowish-brown to brown-black, melting point 180 ° C, soluble in benzene, carbon disulfide, hot linseed oil. Pressed and fused amber is inferior to natural amber in terms of quality and decorative properties and is inexpensively valued.

To change the color of a number of stones, calcination is used for gems and chemical coloring for colored ones. Using the properties of a number of minerals of the quartz group to change color when heated, they were previously calcined in various ways: by baking in bread, covered with ash in a pot, coated with clay, and after complete uniform cooling, the stones acquire pink or gold tones.

To change the color agate and jasper they are kept for a long time (from several days to several months) in a sugar or honey solution, then treated with sulfuric acid and other reagents. Very often agates are dyed, imitating carnelian or sarder (red and brown), onyx (black or brown), chrysoprase (green), chalcedony (blue and blue).

The red color is obtained by impregnation in iron nitrate and subsequent heating. The yellow color is obtained by etching agate impregnated with iron compounds in hydrochloric acid. Black and brown color of agate is achieved by boiling in sugar syrup followed by etching with heated sulfuric acid. Green coloration is achieved by using salts of chromium or nickel nitrate with further strong heating. Blue and blue color is obtained by impregnating agate in a solution of ferrocyanide (yellow blood salt) and subsequent boiling in copper sulfate.

As a result, chalcedony can take on the color of chrysoprase and carnelian, agates - brown and black, and jaspers - enhance the brightness of the color and change it. The color of turquoise can be enhanced with aniline dyes, but even in ancient times, to improve the color of turquoise (CuAl 6 (OH) 2 × 4H 2 O), it was placed in lamb fat or butter. Currently, artificial turquoise is obtained, among other things, by staining the mineral of howlite, calcium borosilicate (Ca 2 [(BOOH) 5 SiO 4]) or chalcedony with copper salts or aniline dyes. In addition, synthetic turquoise ("neolithic", "neo-turquoise", "reze turquoise") is obtained from turquoise crumbs sintered with an adhesive mass, glass, porcelain, and resins.

Glass and plastic imitation stones. Glass and plastic alloys are used as a cheap imitation of gems and colored stones.
Glass alloys are low-melting transparent glass, in which the oxides of lead, potassium and boron are introduced to enhance the gloss. Glass alloys are stained with oxides of copper, selenium, cobalt, uranium, manganese, etc. Stones are obtained by stamping with subsequent processing. To create the effect of playing a stone, a thin mirror layer of silver, fixed with varnish, is applied to the reverse side of it.

Opaque glass alloys can imitate colored stones: turquoise, agate (black), lapis lazuli, etc.

Plastics are imitations of organic stones and some colored stones. The color of the plastic and the transparency are set depending on which stone is imitated. To imitate pearls, milky-white plastic with insignificant transparency is used, followed by coating with a pearl emulsion for a pearlescent shine, amber - unevenly colored, sometimes transparent, yellow tones, coral - opaque, coral, for turquoise - opaque, bluish-greenish, etc. are formed by stamping.

Kazdym A.A.,
candidate of geological and mineralogical sciences,
member of MOIP

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