Emeralds are a green crystal of beryllium-aluminum silicate. The chemical formula is Be3Al2(SiO3). They are hexagonal prismatic crystal with a hardness of 7 1/2 to 8 on the Mohs scale. They are not tough stones and may be broken easily by mishandling or the use of severe chemicals or ultrasonic cleaners. If you own an emerald, be careful of it. Don’t wear it during sports. Don’t have a jeweler clean it in an ultrasonic cleaner as it may shatter.
Emeralds also break under applications of heat and should never be in a ring that is soldered. Under ultraviolet light they may fluoresceslightly, orangish red to red, or they may be inert.
Emeralds come from a number of sources. The best come from Colombia. These are the purest colored and generally the finest stones. The emeralds from Brazil are lighter, have more inclusions and are generally smaller than from other areas. Zambia, Africa, produces some bluish stones and some near-Colombian stones. Zimbabwe is home to a particular emerald known as the sandawana emerald which is generally small with a rich green color. Anything over 1/3 carat is rare.
South Africa produces some low-quality emeralds. Tanzania produces a few very good quality emeralds. Pakistan has just discovered some high-quality emeralds. Afghanistan tends to produce flawed but good colored emeralds. USSR does produce emeralds but doesn’t like to let them out of the country. Australia produces some dubious quality emeralds and North Carolina a few gems. Austria and India occasionally produce emeralds.
Emeralds are not unusual as the word emerald simply indicates an extremely nice version of a fairly common stone known as beryl. It is possible to buy something legitimately called an emerald for about $5 a carat. Obviously this is full of flaws, not transparent and so impure in color it looks more like jade than an emerald. They would never be sold in a jewelry store but emeralds do sell on TV and some of the better magazines for $5 per carat.
Gem quality emeralds range anywhere from $400 to $18,000 a carat, depending upon their quality. As the stones get larger, they become increasingly rare and sell for considerably more money.
Color is a critical factor in emeralds and constitutes about half of the stone’s value (clarity 30% and cut 20%).
Hue describes the primary color and any other colors in the stone. Most emeralds are green hued with a bluish hue also visible, especially the better Colombian-type emeralds.
Tone is the depth or darkness of the color as perceived by the eye.
Saturation is the amount of hue present in any given color.
Depending upon where the emeralds come from, they can exhibit a wide range of color; i.e., Brazilian emeralds are usually lighter toned and less saturated than their Colombian cousins.
The green in the emerald is caused by trace elements of chromium and/or bandium. If the color is very light green, the stone is more correctly referred to as green beryl, not emerald.
Emeralds are often oiled to help their appearance. Normally an uncolored oil such as Merck cedarwood oil is used. The stone may soak in the oil for several days and will actually take the oil in somewhat, helping bring out the color and “wedding” on some of the dry inclusions, making the stone look better.
If one finds an emerald that is mild in color or has a grayish hue, it is a good bet to soak it in oil a couple days and it may regain its green color, not to mention its value.
A more unscrupulous “improvement” is to use dye or oil with color in it. It is possible to influence the color of a stone by having it soak up colored oil.
Other problems with buying emeralds are the fact that there are a number of stones that look like emeralds and overlap colors. Tsavorite, a garnet found in Kenya and Tanzania, looks quite a bit like emerald and has a pure green hue, although it tends to be a little bit more yellowish and never has the blue hue of emerald.
Chrome tourmaline is another stone that looks much like an emerald with a moderately strong green color. Another emerald look-alike comes from Africa and is called chrome diopside. All these stones can, and are, sold as emeralds to the unwary.
Different emeralds from different areas tend to have individually shaped inclusions; i.e., slight pyrite inclusions are typical of emeralds from Colombia although they can be seen in stones from other sources.
A three phase inclusion that shows up under a 1 Ox or stronger microscope, which has a distinctly liquid area, a gas bubble in a solid square rock crystal, salt Iying superimposed on each other inside a jagged edged cavity, is typical of emeralds from Colombia and proves their natural origin.
Tropiche emeralds from Colombia sometime exhibit six fine radiating arms of black carbon inclusions, spoke-like in appearance. Another type of this stone has six arms of emeralds extending from the center of the crystal with a white shaped wedge area in between. When these stones are cut and mounted, they are valuable because of their inclusions.
Emeralds are subject to not only customs duty but market restraints as there is no OSO type organization supporting them. It is possible, if one is smart and has verification equipment, to buy emeralds in other countries, notably South America, and smuggle them to America for profit. Coincidentally, the areas one smuggles emeralds from are the same areas one smuggles cocaine from and these passport stamps tend to yell search me, search me. Some people even go to the trouble of swallowing and then recovering emeralds although obviously, we do not encourage or advise this dangerous practice.
