History & Introduction
Emerald, the green variety of Beryl, is a popular and a valuable
green gemstone. Attractive green colour, which combines with good strength and rare
availability, makes it one of the most expensive gemstones. When they are heated,
it causes the colour to turn blue and transform into Aquamarine. The word emerald
derives its name from the Old French word "esmerlde" or the Greek word "smaragdos",
both meaning green stone. Emerald is the traditional birthstone for May.
Emerald was discovered in the mines of Cleopatra between the Nile and the Red Sea
in southern Egypt. Although, it is not clear that how active the mines were during
the reign of Cleopatra. However, huge quantities were mined in the Roman period
only. Emeralds are unaffected to a great extent to light and heat and they reach
a temperature of 700 or 800 degrees centigrade.
One of the largest and most famous emeralds in the world is the "Mogul Emerald,"
which was discovered in 1695 during the Mogul Dynasty, and it weighs around 217.8
carats. Her Majesty, Queen Elizabeth II, has a fantastic suite of emerald jewellery
which includes an emerald diadem. Emeralds are famous for their flaws. A rare and
unusual form of Emerald, known as "Trapiche Emerald", is characterized by star-shaped
rays that emanate from the centre of a stone in a pattern of hexagonal. Even though
the rays resemble such as asterism, however not according to asterism, they are
not caused by light reflection from tiny parallel inclusions, however because of
the presence of black carbon impurities it is prepared in a star-shaped pattern.
Although, Emerald consist of good hardness, the stone is brittle by nature. It may
get internal cracks if banged hard or if subject to extreme temperature change.
Emeralds, which were treated to mask internal flaws should never be cleaned with
an ultrasonic jewellery cleaner, nor should they be washed with soap or they might
remove the oiling treatment and expose the hidden internal flaws.
Recognise - Almost all natural emeralds contain distinct characteristic
inclusions and mostly they are treated with oil or resin to fill small cracks as
well as fissures. Due to the presence of such flaws as well as oil, which makes
it easy to discern to recognise natural emeralds amongst other alike gemstones.
Artificial light will expose and even the inclusions will get amplified and fractures,
which verify the stone to be a natural emerald. The colour of Emerald is due to
the presence of traces of chromium and vanadium, and to admire the colour natural
daylight is the best condition. One of the easiest methods to identify green emeralds
is to test for specific gravity (density) and hardness. It is a form of beryl, emerald
is harder than apatite, quartz and feldspar, and however it is slightly softer than
spinel, topaz and sapphire. Still emerald is generally more fragile than other beryl,
owing to its nature included state.
Usages - Transparent emeralds are faceted into gem cuts for jewellery,
and are converted into one of the popular jewellery gemstones. Emerald is very sensitive
to pressure and banging. Emeralds that are translucent are cut and polished into
beads as well as cabochons are Trapiche Emeralds.
Availability - Colombia is the main source of the gem emerald.
Egypt is the ancient source of emerald and is also found in Austria, Pakistan, Brazil,
Zambia, Zimbabwe, Russia, China, Mozambique, South Africa, U.S. (North Carolina)
and Afghanistan.
Buying Guide
Colour - In emeralds, the colour is the chief determinant of value.
Emeralds are a medium to dark green to blue-green and sometimes slightly yellowish-green
beryl. Emeralds owe their fine green colour to traces of chromium and/or vanadium
impurities. The most popular and valuable colour is a slightly bluish green in a
medium dark tone with strong and intense saturation, however, too much blue can
decrease the value.
Clarity and Lustre - When the emeralds are cut they have a vitreous
(glass-like) lustre and polished. Though the clarity goes from translucent to opaque
or transparent specimens which are among the most desirable as well as they are
precious. Clarity is desired and inclusions are tolerated more in emeralds as compared
to other gems. Unlike other beryl gems, emeralds often contain inclusions and other
flaws and they are not taken as negative attributes, as they would be for other
gemstones. In general, these flaws are considered part of the character of the stone
and are used to assure the purchaser of a natural stone.
Cut and Shape - Emeralds for this gem only, are cut in a unique
way. The emerald cut is a step or trap cut with a square or rectangular shape with
truncated corners. This style to cut maximizes the beauty and colour of the stone,
while providing security from mechanical strain as well as internal stress. Emeralds
are also cut in many different kinds of shapes that are traditional like pear, oval
and round. Lower grade materials are often cut en cabochon or into beads. Highly
transparent and clear, sometimes materials are cut in brilliant style.
Treatment - Often, oiling has been a common treatment for emerald
generally, it is done right at the mining location. The term 'oiling' refers to
the practice of immersing emeralds in a colourless oil or resin (most often cedar
oil) in order to enhance colour, clarity and stability. This is also often done
using a vacuum chamber to assist penetration. Treatments that are non-standard goes
beyond this with the use of colour oils and epoxy-like resins.
These treatments dramatically improve the look of the gems, but need special care
regarding cleaning and setting. Oil is removed by steam cleaners, solvents and ultrasonic
cleaners, making inclusions, which were hardly visible and stand out in sharp relief.
As emeralds can be restored through re-oiling, the damage seems to be only temporary.
Since 1848 the availability of synthetic emeralds is there. In the 1950s, synthesizing
methods became commercialized and excellent quality synthetics have been made available
since. The term 'Chatham emeralds' is in use for the emeralds that are grown in
labs. There are also numerous emerald doublets found. In many cases, a natural upper-half
is cemented to a glass or synthetic pavilion using an emerald-green paste.
Gemmological Characteristics: