How to differentiate synthetic and natural emeraldBy: Ashish Dimri
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 buyers to:
(a) Purchase laboratory-tested emeralds from a certified jeweler (b) 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 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.
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