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What determines the value of an emerald?
The usual factors that determine the value of all colored gemstones are clarity, cut, color and carat weight. In the case of Emeralds, color and clarity dominate value determination.
All Emeralds have inclusions. These inclusions are characteristics unique to the formation of Emeralds (and some other Beryl varieties) and actually aid in identification of natural Emeralds and separation from created (or synthetic) Emeralds.
These include faceted pyrite crystals, calcite jardin (or garden), spindle shaped cavities, and three phase inclusions with gas bubbles contained in microscopic liquid-filled cavities within the crystal, indicative of hydrothermal formation associated with Colombian Emeralds.
Unlike other gemstones, these characteristic inclusions do not detract appreciably from the value of the Emeralds unless they are distracting or adversely impact the brilliance of the gemstone. Inclusions that are prevalent to the extent that they are distracting and diminish the brilliance of the Emerald will greatly reduce the value of the gemstone.
Which color is the optimum color for Emerald is widely debated, but it can be stated that the more intense the color, the greater the value. In Colombian Emeralds, "Muzo Green" is a term used to define leaf-green colors associated with Emeralds mined in the location of the Muzo mines. Emeralds mined in the Chivor region in Colombia tend to have bluish secondary undertones, similar to those of Zambian origin.
The color hue in Emeralds gives a clue as to origin, but cannot be the definitive test as far as origin, as Emerald hues from these three sources (as well as Brazil) can vary widely within each location. The key to the effect of color on Emerald valuations is color purity and intensity, regardless of source location.
Cut and carat weight have a decidedly secondary effect on Emerald values. Very large faceted Emeralds, in excess of ten carats, are quite readily available if one is willing to settle for lighter tones, less intense color or reduced brilliance. The same cannot be said for Diamonds, Rubies and Sapphires. However, very fine grades of Emerald over one carat are very rare and with respect to value may rival and sometimes exceed that of Diamonds of equal carat weight and grading
What is an emerald?
Emerald is the green gemstone variety of the mineral Beryl (the blue variety of the mineral Beryl is Aquamarine). Beryl is beryllium aluminum silicate, with the known chemical composition of Be3Al2Si6O18.
Emerald crystals are hexagonal in nature. Large Emerald deposits are currently mined in Colombia, Brazil, and Zambia. Emeralds are mined throughout the world (Pakistan, Afghanistan, Russia, Australia, United States) but these are the three major sources. The Zambian and Brazilian Emeralds may be colored due to the presence of vanadium, whereas Colombian Emeralds usually achieve their coloration from the presence of chromium.
Emeralds have been treasured as adornments in the form of jewelry for centuries. Emeralds are at least twenty times more rare than diamonds, but in the finest grades sell for approximately the same per-carat price as diamonds. Emeralds are readily available in lesser grades and even very large sizes, but are exceedingly rare in fine grades in any size.
Widely recognized as the Birthstone for May and Astrological affiliation with Cancer (June 22 / July 22), Emerald is also the celebrated gemstone of choice for 20th and 35th Wedding Anniversary. The Emerald continues to be one of the most popular of precious gemstones, rivaling Diamonds, Rubies and Sapphires
Colombian emeralds will typically be the most expensive followed by Brazilian and Zambian stones. The reasoning is related to the color. Colombian emeralds get their color primarily from the trace amounts of the element chromium which is responsible for some of the purest greens in gemstones. Brazilian emeralds get their color primarily from trace amounts of the element vanadium and Zambian emeralds get their color from iron. Brazilian emeralds typically have a slight brown or gray cast and only sometimes match the pure green hue that many Colombian emeralds offer and Zambian emeralds often appear too blue due to their iron content. In reality though, emeralds from all three sources may be colored by more than one element
How should I care for my emerald?
Emeralds are frequently bezel-set to protect them from bumps and knocks. Many jewelry designs for Emeralds may have them surrounded with accent stones such as Diamonds or White Sapphires, to add beauty and to protect them from side impacts. Although Emeralds have a high hardness rating and are not easily scratched (7.5 to 8.0 on Mohs scale), they can be chipped from impact.
Emeralds typically have inclusions. The inclusions in Emeralds may be solid, liquid or gas filled. Emeralds are typically oil-treated to improve the clarity and luster. Cleaning of Emeralds should take into consideration these facts. Although Emeralds are a fairly hard gemstone, this does not mean that they can be subjected to harsh cleaning.
Emeralds should never be cleaned with steam or any cleaning solution that contains petroleum distillates or any other organic solvent, even if the cleaning solution is a recommended "jewelry cleaner". Most of these are not compatible with the oil treatment of Emeralds.
Emeralds should not be placed in ultrasonic cleaning equipment at all, either, and should not be exposed to high heat. A good rule of thumb is that if the cleaning solution you use is too hot for you to put your hand in, you should not place your Emerald in it.
An Emerald should be cleaned gently with a warm, mild detergent solution and a very soft brush, such as a worn-out toothbrush. We recommend soaking your Emerald in a dishwashing-detergent solution similar to that used to clean regular household dishes, for approximately ten minutes. Then, clean the emerald and mounting with a soft brush. The Emerald should then be rinsed with warm water, and patted dry. You should not leave your Emerald immersed in the cleaning or rinse solution any longer than is necessary. Cleaning should be done no more frequently than is necessary, and in no cases more than several times a year.
After many years of wear, you may wish to have your Emerald re-oiled. Most local Jewelers are familiar with this process and can provide this service