Recently chosen as Pantone “Color of the Year” for 2013; emeralds are among the most precious of natural gemstones, alongside rubies, sapphires and diamonds. Emerald is a type of the mineral beryl. Its green color is a result of small amounts chromium and sometimes vanadium within the gemstone. Depending on the amount of these elements, the emerald can appear light green to a very deep, dark green. Emeralds are by far the most stunning and popular of the green color gemstones. For centuries, they have been among the most sought after and valuable gemstones symbolizing rebirth and love.
The color of a gemstone is considered to be the most defining characteristic when evaluating the overall appearance. Color is the most important factor when pricing emeralds and is broken down into three components: hue, saturation and tone. An ideal emerald for an engagement ring is well saturated and bright.
Emeralds are found in hues ranging from yellow-green to blue-green, with the primary hue being green. The most desirable emerald colors are bluish green to green, with vivid saturation and medium to medium dark tone. The most prized emeralds are highly transparent with even color distribution and no eye visible color zoning. Secondary hues found in emeralds are usually yellow and blue however, when the hue is too yellowish or bluish the stone is no longer considered an emerald but will be considered a different beryl. (Gray is the saturation modifier or mask found in emeralds.)
Beryl is a relatively common mineral and is associated with many gemstones. For instance, beryl that is yellow or orange is usually called Heliodor, pink or salmon colored beryl is called Morganite and the rarest type of beryl, bixbite is a deep, intense red. Emerald usually comes in a deep, intense green. However, it is sometimes found as a light green or even to have a tinge of yellow in the stone.
Emerald tends to have numerous inclusions and surface breaking fissures. Unlike a diamond, where the loupe standard, i.e. 10X magnification, is used to grade clarity, emerald is graded by eye. Thus, if an emerald has no visible inclusions to the eye (assuming normal visual acuity) it is considered flawless. Stones that lack surface breaking fissures are extremely rare and therefore almost all emeralds are treated, "oiled", to enhance the apparent clarity. The most expensive emeralds are eye-clean stones of an intense primary green hue with no more than 15% of any secondary hue or combination of a medium-dark tone.