How to differentiate synthetic and natural emerald

by Ashish Dimri

Synthetic emeralds are produced in Germany, France, and United States of America with flux growth and hydrothermal processes in laboratory. These are expensive methods and difficult to yield major results .It is mentioned that the first synthetic emerald appeared in last part of last century.

Introduction

Right from beginning of this world, the emerald has fascinated the world. It was and still is the favorite gemstone of dynasties and elite classes around the world. In the past, Indian rulers like Shah Jahan were so enamored with emeralds that the monument to his departed wife was decorated with beautiful inlays of emeralds and other precious stones. That magnificent monument is known as ‘Taj Mahal’. Egyptian pharaohs used them in crowns and many were even buried with them. It is considered an auspicious gemstone and is believed to ward off evil influences from our life. Though much has been written about it, people still find it difficult to differentiate between natural and a synthetic emerald.

Gemologists explain that natural emeralds are formed when the natural forces of the earth apply heat and pressure in while synthetic emeralds are formed when heat and pressure are applied to minerals in a laboratory. Synthetic emeralds in other words are laboratory-grown gems and are not mined from the ground like natural emeralds. These are also less expensive compared to natural emeralds. Therefore, those who cannot afford natural emeralds but aspire to own the gem purchase their inexpensive counterparts.

Emerald is the deep –green colored variety of beryl. It has a conchoidal fracture and delicate tenacity therefore it is sensitive to pressure and heat. It is so green that the famous roman scholar ‘Plini’ called it “greener than green.” Being extremely beautiful, emerald has always been patronized by kings and elite classes in the past. People are mystified by its green light. Few know that its green color is caused by impurities from chromium and vanadium. It is said that the finest emeralds are sourced from Colombia especially in the Mura and Cosquez mines but recently deposits have also been found in Zambia, Brazil, Russia and Pakistan. The finest emeralds are known to be transparent but commonly may also have inclusions.

Synthetic emeralds are produced in Germany, France, and United States of America with flux growth and hydrothermal processes in laboratory. These are expensive methods and it is difficult to yield major results . One of the reasons is an extremely slow productive methodology used in synthesizing emerald.

It is always difficult to differentiate between natural and synthetic emerald because they both have the same chemical composition and crystal make-up. Previously synthetic emeralds were tested with the Chelsea color filter to find out the difference between natural and synthetic emerald. But it was capable of producing only limited results. After much research reputed gemologists and jewelers concluded that the difference between natural and synthetic emeralds could be found out by the assessment of specific gravity and refractive indices of emeralds. In simple words, specific gravity of emerald is its weight in air divided by the loss of its weight in water. It is tested with density meter, a scientific instrument. Refractometer is a scientific instrument that calculates the speed of luminous rays arising from the stone. Refractometer is also used to check the indices of refraction of the stone.

Major Differences

Expert gemologists have found out that the major differences between synthetic and natural emeralds are:

• (a) Specific gravity of a synthetic emerald (2.66) is lower than natural emerald (2.70-2.78) and refractive indices of a synthetic emerald (1.565) are lower than natural emerald (1576-1582).
• (b) Flux growth and hydrothermal processes can produce synthetic emerald and due to them it shines unexciting red in ultra violet light which one does not get in a natural emerald.
• (c) Synthetic emerald possesses feathery inclusions, which are not to be found in natural emerald
• (d) Natural emerald produces green light because of impurities but in synthetic emerald this is not the case.
• (e) Clarity of natural emeralds can be enhanced by oiling but in synthetic emerald this cannot be done.

Emeralds are the second most precious gemstones after diamonds. Since the global market is flooded with synthetic and fake emeralds, veterans in this field always insist on extensive tests to distinguish a natural emerald from a fake one. International gemologists have ardently appealed to those who are involved in buying and selling emeralds to advise their clients to seek the help of professional gemological centers or laboratories to check the emerald for authenticity.

World-renowned gemologists advise for buyers

• Purchase laboratory-tested emeralds from a certified jeweler
• Get a certificate from the source of emerald for its identity. Major emerald producing countries like Columbia and Brazil have associations that certify exporters and sellers for quality control.

Scientific methods to distinguish a natural emerald

Any serious buyer of emeralds must avail services of gemologists because gemologists use a number of laboratory tests to gauge the true identity of natural and synthetic emerald. At the outset, they use a hand lens to check visual features like clarity and binocular microscope for features such as color zoning, growth, and inclusions. As it is difficult to distinguish a natural emerald from a synthetic one, a scientific instrument known as a spectroscope is used. The spectroscope is an instrument that allows the observer to relate a gemstone’s color to its absorption spectra.

Raman spectroscopy

Raman spectroscopy is an advanced method to judge fingerprinting inclusions of synthetic emeralds. Later on, gemologists often use advanced testing instruments like energy-depressive x-ray fluorescence system (EDXRF) for further investigation. These advanced tests are performed by trained gemologists, and only after intensive testing conclusions about natural and synthetic emerald can be made.

It is advisable to be careful with emerald because it is not only precious but one cannot differentiate between a natural and synthetic emerald without thorough knowledge of the subject. Therefore those who are buying it must first know about specific gravity of a natural emerald that is often between 2.70 to 2.78 and also refractive indices that is always between 1576 to 1582.They should also insist on a certificate containing particulars like source, carat weight, color and clarity from the jeweler.

Journey of an emerald from mines to jewelry

by Ashutosh Roy

The gemologists add an importance to polishing the stone, as the selection of abrasives is very crucial in polishing emerald because the abrasive may penetrate the inclusions to creep inside it.

The name of Cleopatra is very closely associated with an Emerald, as Cleopatra not only had her own emerald mines but prized emerald more than the any other gemstone. The fact of life is that it is not only Cleopatra, gemologists believe that the popularity of the Emerald will be at its zenith as long as the universe exists, because of its eye catching Green colour of Emerald is synonymous to life. At times the colour of Emerald is compared with fertility or ‘being evergreen’ also.

courtesy: MineralMiners.com

Emerald is the birthstone for people born in May and is also an anniversary gem for the 20th and 35th years of marriage. The green colour of Emerald is supposed to bring vitality to the wearer’s health and mind. Archaeologists have discovered the traces of Emerald in Egypt dating back to 3000 B.C. Emerald also finds its place amongst the most ancient cultures in India. The ancient kings and queens of India used to preserve emerald as a treasure, because Emerald not only neutralizes the evil effect of Mercury but also its cost was too high.

There was a time, when people used to compare every green colored gemstone to Emerald but gradually science has been able to identify and segregate Emerald from the rest of the crowd. The presence of chromium and traces of iron generates the elegant green colour of emerald.

Emerald in originality is from the mineral beryl, the brilliant crystals. The green variety is called the Emerald. A pure clean Emerald is highly expensive. An inclusion free Emerald of one carat costs $600. It varies significantly with the variation of colour and clarity. The hardness measures7.5 to 8 on the mohs scale..

If your head aches continuously why don’t you try out an Emerald?. Remember emerald has been used as a healing agent against bladder and kidney functions due to its cold green colour. The green colour is even said to fight your eye-problems and the digestive system also.

The best quality Emerald comes from Muzo, Coscuez, Chivor of Columbia. The Emerald Hollow Mine near Brushy Mountains, California, is open for public. In the recent past the significant portions have been extracted from the Maripi town deposits also. Emerald deposits have been found in various parts of the world, which includes Brazil and Africa. The Asian countries like India, Pakistan and Afghanistan have been also had its own supply of emerald. Russia and Egypt had been the key sources of Emerald over a period of time. Emeralds are cut from Matrix and the colour variation of emerald is due to the variation of its Chromium component but partially depends upon the extracting methodology also. Emerald is extracted by two very common methods namely the tunnel and the open pit methods. Cutting the crystal proves to be a very difficult process as a hard rough stone inherits many inclusions.

Skilled craftsman often reveal the optimum brilliance and vibrancy by immaculately cutting the precious gemstone. Remember a small diversion in orientation while cutting can affect the value of the gemstone in its final stages. All emeralds are placed in oil immediately after the extraction phase to get rid of the inclusions. Its shape can be octagonal, round, oval or any other imagined by the designer. The colour can vary depending upon the cut and the facets of the stone, while shaping. The only point is that it requires the cutter’s rapt attention to yield the best results. The nitty-gritty of step-cut of emerald is so cryptic that has been labeled as the Emerald Cut. Sometimes Emeralds are processed further to elude the cracks and dyes are applied to enhance its effects. Indians may feel pride of the fact that the pink city of India is the key place for emerald processing. Most of the countries send their emeralds to Jaipur for processing.

The gemologists add an equal importance to polishing the stone, as the selection of abrasives is very crucial in polishing emerald because the abrasive may penetrate the inclusions to creep inside it. The price largely varies on the brilliance of its green crystal. When the rays parse through the hexagonal structure an emerald transmits bright spraying rays. But caution! A light green emerald is cheaper.

Sometimes epoxy resins are used for treating of emeralds. To test its authenticity, you may place the emerald under running tap water. At this stage a mirror image will give you the authenticity of the gemstone. Now, if you want to prolong its lifespan as a stunning sparkling crystal then clean it with a little warm water. Don’t allow other rough gemstones to affect its sheen by coming in close contact to its surface. Use light soap to rinse it while taking care not to stain the gemstone. Try to prevent it from the onslaught of direct heat or strong light or radiation and beware of unwanted scratches to your precious ornament. Use velvet or a soft fabric lined jewelry box to keep it safe.

Astrologists suggest wearing emerald in Gold on the little finger to protect you from mental distress or frequent injuries, loss of wealth or property and to induce positive vibes. Astrology does not restrain you from wearing a dazzling Emerald or Diamond bezel-set necklace. An oval shaped emerald earring is still at the height of its fashion. An oval shaped emerald or diamond flower pendant can draw attention at any social gathering. A ring consisting of a genuinely oval shaped emerald with brilliantly cut diamonds can add be the ideal for your engagement. An emerald earring in 14k yellow gold with posts and push back not only makes it safe but also dazzles to become the draw for any evening out. A nicely hand carved emerald beads necklace by Chinese craftsmen always adds the human touch in your jewelry collection.

So, why don’t you try out an Emerald to increase your level of intelligence or to own a fine physique combined with powerful memory? If the stone even cannot bring wealth for you, it will generate a good investment return at least.

Emerald Gemstone Varieties

by Madhubanti Rudra

Emeralds differ in shine and color depending upon the locale of its mine. It is only the Columbian emerald that has the characteristic vivid, slightly bluish green tones of medium-to-medium dark color. Deposits of the stone are also found in other parts of the world such as in Zambia, Zimbabwe, Madagascar and Nigeria. However Columbia and Brazil are the leading producers of emerald today.

Summary: Green is life. Green is happiness. So is emerald. For ages it has been a regal choice. But the common men are often confused at the time of buying this magnificent gemstone. Knowledge about the emerald classification will help you to sail through the bargaining process for the right stone. So read on the article to learn about different types of emeralds

“He who possesses it shall enjoy special protection of God”-reads a talismanic Mughal emerald. This birthstone of the month of May has been the passion of Cleopatra and love of the Mughals. Along with ruby, diamond, and sapphire, emerald is an important member of the big “awesome foursome” and has long been attributed healing and mystic prowess. Being associated with the planet Mercury, emerald is traditionally believed to cure diseases like forgetfulness, epilepsy, stammering and even insanity. Attributing mystic qualities to this gem, it is said that this piece of stone brings foresight and wisdom to the possessor.

Emerald (Be3Al2Si6O18) is the grass-green type of Beryl. Mostly it occurs in mica schists of metamorphic-hydrothermal origin. The formation of emerald involves a natural process known as exometamorphism. During this phenomenon if the basic rock contains the elements chromium or vanadium small quantity of it might get incorporated in the structure of beryl. This gives the rock its gemlike green color. Varying amount of iron also alters the color of the rock. It has a hardness of 7.5-8 and a refractive index of 1.57-1.59. However it is not a gem recommended for ‘everyday’ use since it falls in the category of soft stone. The real worth of the gem rests in its green dazzle and variations in shades. They range in color from slightly yellowish green to darker bluish green. The cut of the stone is also significant. Although faceted emerald can have round, pear, oval shapes the emerald cut, that is, octagonal shape is most preferred. Inclusions are almost an accepted fact in emeralds.

Emeralds differ in shine and color depending upon the locale of its mine. It is only the Columbian emerald that has the characteristic vivid, slightly bluish green tones of medium-to-medium dark color. Deposits of the stone are also found in other parts of the world such as in Zambia, Zimbabwe, Madagascar and Nigeria. However Columbia and Brazil are the leading producers of emerald today. The mines of Egypt, which supplied emeralds to Cleopatra, are not much into production today. Among the foremost consumers of emerald are USA and Japan who buy 75% of the world’s cut emerald.

COLUMBIAN EMERALD GEMSTONE

Columbia is the foremost producer of emeralds. Both in terms of quantity and in terms of quality Columbian emeralds lead the world. The transparency, crystallization and fire identify a Columbian emerald. It is the deep green shade of Columbian emerald that is taken as standard.

History depicts that when the Spaniards conquered America the Egyptian mines were no longer producing emeralds. The conquest brought the Spaniards into a land laden with one of the world’s most precious stones. It is primarily the rich colour and proverbial quality of emerald from the Andes mountain ranges that has distinguishes Columbian emerald from African or Brazilian emerald. It is described as ‘green on top of green’. In the Columbian mines emeralds are worked by hand and plucked from carbonaceous shale. Muzo and Chivor are two of Columbia’s most important mines. Emeralds mined in Muzo are slightly yellowish whereas those from Chivor are bluer. It is also believed that there is a symbiotic relationship between Columbian emerald and the gold of the country. The combination is therefore splendid. It is left to your imagination what jewellery might be produced by the country’s craftsmen.

BRAZIL EMERALD GEMSTONE

Brazil has been supplying emerald to the world market since the 1980s. Typical Brazilian emeralds are lighter and yellowish

AFRICAN EMERALD GEMSTONE

African countries like Zimbabwe, Zambia, Madagascar and Nigeria have deposits of beryl and are the second most leading producer of emerald. Unlike Columbian emerald, African emerald lacks the intensity of green colour. Due to the presence of a higher percentage of iron in these emeralds the green colour gets blunt and a grayish tinge takes over. Therefore it is described as ‘green on top of grey or brownish grey’.

Emerald from Zambia often has the defect of being ‘overblue’ that is when viewed under incandescent bulb it appears to be bluish. It might be mentioned here that when emerald was first discovered in Zambia it was not considered emerald at all. This was because although it was bright it had a lighter to medium hue. The confusion was deepened by the fact that it had much less inclusions and could be doubted as synthetic. Later on this doubt was cleared and Zambian emerald made emerald affordable to a lot of people..

Emeralds from Zimbabwe are smaller is size and lighter in shade. However the term ‘African emerald’ is a misnomer. It simply denotes green fluorite.

Some of the other countries, which produce emerald, are Russia, India and Australia.

RED EMERALD OR BIXBITE

This gem which is basically formed out of the mineral berl takes its colour due to the presence of manganese. It is found only in a few deposits of Utah’s Wah Wah mountain. This makes it one of the rarest gems of the world all the more so if it is facetable.

SYNTHETIC EMERALD GEMSTONE

The synthesis of emerald began in the 1930s when it
was done by a process known as Farben and the Chatham processes. However the process did not run out to be commercially much viable. Later on in the 1960s another process known as hydrothermal flux process began to be used in the production of synthetic emerald. In this method crystal nutrients are dissolved in an acidic solution of water and chemicals at a very high temperature and pressure. It is then allowed to crystallize in a cooler chamber of the reactor. This method of emerald production proved to be much viable and by 1980 as much as 500,000carats of gem had been manufactured through this process. Manufacturers Biron, Chatham, Kyocera, Gilson, Inamori, Farben, Lechleitner, Linde and others produce synthetic emeralds today.

Emerald Identification

by Erum Qureshi

Step by step lab procedure to identify the green stone emerald in scientific manner. Learn from an expert, how the Refractive Index, Double Refraction, Absorption Spectra is used to determine the stone type.

Emeralds belong to the species Beryl

The property that distinguishes an Emerald from other Beryls is the characteristic deep green or bluish green color caused by the presence of chromium. All Beryls of other colors of gemstone quality are called precious beryl and not emeralds. The first thing that a trained gemologist looks for is the color.

If the color of the stone is deep green (Emerald green), green or even slightly yellowish-green, then tests will be conducted to specifically identify it as an Emerald.

Step 1: Determination of Density (Specific Gravity or S.G):

Specific gravity indicates the ratio of the weight of a specific material to the weight of the same volume of water. It is also expressed as density and is measured in grams per cubic centimeter.

Although a determination of the density is useful, specialists rely on optical procedures for taking the final call on the determination of the gemstone.

The density of the stone is calculated by placing the gem in a beaker filled with heavy liquid or high-density liquid.

This method works on the idea that an object will float in a liquid of higher density, sink in a liquid of lower density and remain suspended in a liquid of the same density. Sets of high-density liquids are sold commercially, but need to be handled with care due to their toxic nature. Since the density of emeralds is between 2.67 to 2.78 if the stone is an emerald it will float in a liquid of density 3.20 and remain suspended in a liquid of density 2.67.

Step 2: Refractive Index (R.I)

Refraction of light occurs when light rays leave one medium and enter obliquely into another at the interface between the two media. The amount of refraction (called the refractive index) in the crystals is specific for each gemstone. It can therefore be used in the identification of the type of stone.

The light refraction is measured in a Refractometer by placing the gem face down in the apparatus with a small amount of contact liquid (Liquid available in the market for gem testing).

The values can be read from the Refractometer scale, however testing is only possible up to a value of 1.41 to 1.81.

For cabochons (gemstones cut with an even stone surface and no facets, a cut synonymous for opaque gemstones) spot readings can be taken if the stone is transparent to semi-translucent. If the purported stone IS an emerald the reading will fluctuate between 1.56 and 1.60. Stones other than emeralds will exhibit different R.I. For e.g: the green andradite garnet (also called Demantoid and commonly confused with emerald) has an R.I of 1.88 and therefore will not show a reading at all in the Refractometer (since a Refractometer will only take readings up to 1.81). Tourmalines, also commonly confused with emeralds have an R.I between 1.61 and 1.66, which will again indicate that the said stone is NOT an emerald.

Determination of the R.I however will not help in distinguishing between natural and synthetic emeralds.

Step 3: Double Refraction (D.R)

Just as a ray of light is refracted when entering the crystal of a gemstone, it is at the same time divided into two rays. This phenomenon is known as double refraction. It is expressed as the difference between the highest and lowest refractive index and can be useful in identifying gemstones. Some gemstones are singly refractive and some doubly refractive and to determine this, a polariscope is used.

Emeralds are doubly refractive gems therefore, when viewed in a polariscope, show the characteristic DR effect, which is alternate dark and light effects when the stone is rotated 360 degrees.

Step 4: Pleochroism

When viewed in different directions some gems appear to have different colors or depth of color. This is caused by the differing absorption of light rays in double refractive crystals. Where two main colors can be observed (tetragonal, hexagonal and Trigonal crystal systems) we speak of Dichroism or Pleochroism (a descriptive term for multi-coloredness).

The instrument for observing Pleochroism is the dichroscope.

The crystal structure of emeralds is Hexagonal / hexagonal prisms and when viewed through the dichroscope it will appear Dichroic (that is two definite colors can be observed- distinct green, blue-green to yellow-green).

Step 5: Absorption Spectra

The absorption spectrum of a stone consists of the bands or lines that appear in the spectral colors of light as they emerge from the gemstone.

The instrument used to determine the wavelength of the absorbed light is the spectroscope.

The wavelength is measured in nanometers (symbol nm) or Angstrom symbol A. Like most gems Emeralds have a very characteristic, almost unique absorption spectrum. When viewed through the spectroscope the absorption spectrum of an emerald will show this characteristic black vertical lines or bands.

The absorption spectra of natural emerald (in nanometers): 683, 681, 662, 646, 637, (606), (594), 630-580, 477, 472.

The absorption spectra of synthetic emerald: 683, 680, 662, 646, 637, 630-580, 606, 594, 477, 472, 430.

(Strong absorption lines are in bold letters; weak ones are in parenthesis.)

This characteristic absorption spectrum determines without any doubt the stone or glass used to imitate the emerald. By this method one can easily differentiate between gems of the same density and similar refractive index.

Rough stones, cabochons and even set stones can be effectively tested by this method.

Microscopic Examination

(Image courtesy: Orbital Joe)This is undoubtedly the most important and deciding test in determining the authenticity of any gemstone. Gemstones contain foreign matter, or some kind of dislocation or irregularity in the crystal lattice. These are visible to the naked eye or under magnification and are known as inclusions.

Inclusions are not accidental but are subject to strict conformities with natural law, they can tell a lot about the origin of the gemstone and also help in identification.

The final step to identifying any gemstone is the physical examination of the specimen with a 10 X loupe and / or a microscope.

There are forms of inclusions specific to every gemstone as also to its imitation. Natural emeralds when examined under a microscope show two phase (liquid and gaseous) or three-phase (crystal, liquid and gaseous) inclusions. These appear as tiny black inclusions, these are embedded in the crystal during the formation of the mineral. Some other inclusions are needles and crystals. Some typical inclusions are characteristic to the place of origin of the emerald.

For example tremolite needles and mica plates with well-rounded edges in Russian emeralds, typical three-phase and inclusions of well formed pyrite crystals, actinolite and comma-shaped inclusions in Indian emeralds.

Synthetic emeralds under high magnification will show gas bubbles (which appear as soap water bubbles) and traces of unmelted powder and swirls as inclusions.

Fluorescence

Another test to determine synthetics from natural emeralds is exposing it to Ultraviolet radiation (or UV rays).  Synthetic emeralds transmit UV light more than natural emeralds.

There are two common ultra-violet rays used for fluorescence. Those are short wave and long wave rays. Short-wave rays are ones with smaller wavelengths but with lighter frequencies and power in terms of penetration to the gemstone. Exposed to short-wave rays emeralds may show reddish fluorescence and when exposed to long-wave rays neutral fluorescence.

Alternatively the Chelsea Filter (an apparatus used by gemologists through which when an Emerald is viewed it appears red due to its chrome content) may be used to determine specific red fluorescence under short wave.

Consumers should also beware of fluorite and chrome Diopside, which are very close imitations of emeralds when set in jewellery.

References:
Gemstones of the World by Walter Schumann
Gems by R Webster