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.