Since the time of Cleopatra, emeralds
have epitomized the of color in green gemstones. It would be easy to
question this statement if all one had seen of emeralds were the
commercial, (and poorer,) quality stones which abound on home
shopping networks and in some jewelry stores. A fine emerald,
though, is a truly breathtaking sight and is well deserving of its
placement in the traditional "big four" along with sapphire, ruby
and diamond. Emerald is the birthstone for May and for commemorating
the 20th and 35th wedding anniversaries.
... The center of world emerald mining
is in South America with Colombia and Brazil as major producers. The
African mines that supplied Cleopatra's passion have long since been
played out. However, today the African continent is second only to
South America in production, with mines in Zambia, Zimbabwe,
Madagascar and Nigeria.
... Each of these world locales
typically produces a certain color, size and clarity -- so much so
that the term "Colombian" emerald has often been enthusiastically
used to describe vivid, slightly bluish green stones of medium to
medium dark color, no matter what their actual geographic origin.
Likewise, emeralds of lighter color are sometimes called
"Brazilian", even if they were mined in Africa. The USA and Japan
together purchase more than 75% of the world's cut emeralds.
... Emerald, by definition, is a medium
or darker green to blue green beryl, in which the green color is
derived from impurities of Chromium, Vanadium, or a combination of
both. Before 1963 the definition was limited to Chromium containing
stones, but the discovery of a large deposit of Vanadium colored
stones in Brazil led to modification.
... Varying amounts of iron will affect
the color as well, with more atoms of this impurity increasing the
bluish tones. In a situation similar to that which exists with the
boundary between pink sapphire and ruby; there are chromium colored
stones of light to medium light green color which are sometimes sold
as emerald, but which are more correctly considered green beryl.
Geological conditions were right, it seems, in Colombia to produce
exactly the slightly bluish green shade and strong saturation that
make stones from that locale the epitome of the variety.
... Emeralds are considered a "Type
III" gemstone by GIA which means that they are virtually always
included to one degree or another. Because of this designation, a
clarity grade of "very slightly included" for example, refers to the
normal range for emeralds, not for all gemstones. Well over 90% of
the emeralds in commerce have been treated to minimize the
appearance of the inclusions.
... The industry practice for
treatment, (and that which is considered "standard" by AGTA,) is
"oiling". This term refers to the practice of immersing emeralds in
a colorless oil or resin. Often this is done using a vacuum chamber
to assist penetration. Non-standard treatments go beyond this to
using green colored oils and hardened, epoxy-like resins.
... These treatments dramatically
improve the appearance of the gems, but necessitate special care in
cleaning and setting. Steam cleaners, solvents and ultrasonics can
remove the oils, making inclusions which had barely been visible
stand out in sharp relief. Luckily, it is possible to have emeralds
... The inevitable inclusions are more
than a aesthetic consideration, as they can reduce the structural
integrity of the gem as well. Beryls, in general, are good jewelry
stones, with a hardness of up to 8 and no troublesome cleavages.
Because of the inclusions, emeralds are generally more fragile than
other beryls and must be treated more gently.
... Emerald imitations often
encountered in the marketplace include: glass, YAG, synthetic spinel
triplets, green cubic zirconia, and beryl triplets. Within the last
fifty years two major processes have been developed to produce "lab
created" emeralds, or synthetics. If you've seen and priced man-made
emeralds you might have wondered why they are so costly compared to
CZs or some types of synthetic sapphires. Both the flux and the
hydrothermal methods of production require costly equipment and are
energy intensive. They take a long to time produce and have a low
yield of cuttable gems.
... Some of the first lab created
emeralds on the market weren't convincing because they were so
clean, but the sophistication of today's consumer has led to a trend
toward more naturally included looking synthetics. Although this
improves their acceptability, it does make it a little more
difficult for gemologists and appraisers to prove natural origin.
Fortunately, there are signs, particularly regarding the types of
inclusions in a gem, which can conclusively verify natural versus
... Like many stones, the per carat
price of fine quality emerald escalates rapidly with size. For
example, a recent price guide lists a fine quality, 3 carat
Colombian stone as six times more valuable than three equivalent
quality 1 carat stones.
... Value factors hinge largely on
color with nuances of saturation and hue affecting price to a
significant degree. The most desirable color is a slightly bluish
green in a medium dark tone with strong to vivid saturation. Clarity
is important, but inclusions are tolerated more in this variety than
virtually any other gem. Top quality, unenhanced stones, (with
certification,) can bring as much as 50% more in price than treated
stones of the same size, color and clarity.
Facts about Emeralds
REFRACTIVE INDEX ~ 1.57 - 1.59, varies with source.
HARDNESS 7.5 - 8
SPECIFIC GRAVITY 2.68 - 2.78
HEAT SENSITIVE No
Poor to Good, depending on the integrity of the gem.
SPECIAL CARE INSTRUCTIONS Emeralds usually have internal
fracutres, so clean with warm or room temperature soap and water.
Avoid wearing gem where it will get rough treatment.
Oiling, common. (Oils and epoxies are used to fill fractures, which
reduces their visibility.