Guide to Emerald

History, Lore and Appreciation

Emerald’s appearance and color make this gemstone instantly and universally recognized. The rich, green hue has also been the primary reason for the gemstone’s tremendous popularity throughout history. In many instances, the word “emerald” is used to define saturated variations of green, such as the lush vegetation of the “emerald isle,” or an “emerald green ocean.” Marbode, the medieval poet and Bishop of Rennes, France, loved emerald’s color, causing him in 1120 CE to have observed the following:

“Of all green things, which the bounteous earth supplies, Nothing in greenness with the emerald vies.”

Hundreds of years earlier, the naturalist Pliny the Elder (23 CE to 79 CE) declared his sentiments as well:

“We delight in feasting our eyes on the pleasant green grasses and leaves, but the enjoyment of beholding an emerald is incomparably greater, for its green is most soothing.”

Pliny was one of the first to classify gemstones, including emerald. But appreciation for emerald was evident long before him. It is thought that emerald was first used as a gemstone circa 3500 BCE, and later during the first dynastic reigns in Egypt and so, conceivably for thousands of years, Egypt was the world’s main emerald source. Actress Elizabeth Taylor, who played Queen Cleopatra on film, was equally enamored with emerald as the Egyptian she portrayed. Aside from wearing magnificent emerald jewelry throughout her life, Taylor used the color and popularity of emerald to once launch a perfume.

Emerald represents rebirth and eternal spring. Its color denotes honesty, and integrity; finally, emerald has long been thought to be capable of soothing one’s eyes. The Roman Emperor Nero is said to have watched gladiator fights through emerald slices for that very reason! However, that reference from Pliny the Elder’s observations remains the subject of some debate today.

Birthstones and Anniversaries

Emerald is the birthstone for the month of May. It is also considered a 20th wedding anniversary gem.

Description and Properties

Emerald is a variety of the beryl species of minerals and has the following chemical formula: Be3Al2Si60188

Beryl also includes the following gemstone varieties: aquamarine, morganite, red beryl, green beryl, heliodor and goshenite (Note: more about the beryl gem varieties in the chapters, Aquamarine and Other Beryls). Emerald (and other beryls) typically grows as hexagonal (six-sided) crystals.

Color: Vibrant, deep green color that is often described as very strongly bluish green through green.

Refractive Index: 1.577 to 1.583 (±0.017) Birefringence: 0.005 to 0.009

Specific Gravity: 2.72 (+0.18, -0.05)

Cause of Color: Chromium generally, sometimes vanadium and sometimes a combination of chromium and vanadium.

Mohs Hardness: 7.5

Internal identifying characteristics: multi-phase inclusions, mica platelets, calcite, actinolite, and pyrite inclusions. In Colombian emeralds, jagged or blocky multi-phase inclusions are sometimes seen. A roiled appearance from columnar growth, called gota de aceite, which translates drop of oil, is a desirable trait some rare emeralds may exhibit. Inclusions in emerald are considered customary and expected. While gems with no eye visible inclusions do exist, they are extraordinarily rare. Some inclusions in emerald are informally referred to as jardin, (meaning garden in both French and Spanish) and may consist of networks of tiny liquid filled inclusions and minute fissures that permeate the gem, lending it the appearance of a lush garden – hence the term. These inclusions also impart the emerald with a distinctive, somewhat hazy appearance because they diffuse and spread light through the gemstone. Included crystals, such as pyrite, are fascinating to examine through a microscope, and provide positive proof of the gemstone’s natural origin. Buyers should check for occasional larger fissures (especially those located at corners where a prong might be placed). Because of potential durability issues, such stones should be avoided.

Emerald is durable enough to bring joy to successive generations if handled with appropriate care. Conversely, lighter beryls, such as aquamarine and morganite, are very often eye-clean (viewed without magnification) even in sizes larger than 5 carats.

Treatments

The minute fissures that are often found in emerald lend themselves to a form of treatment aimed at diminishing or masking their appearance. These fissures often reach the surface and may be filled with substances including oils, resins and polymers. The manipulation of an emerald’s appearance (other than cutting or fashioning) was first described by Pliny and as such has probably been practiced to varying degrees for centuries. Because introducing substances into emeralds may substantially change their appearance (and perceived value) the presence of these kinds of treatments must be disclosed from the seller to the buyer along the supply chain. Special care considerations need to be explained as well because oils and some resins may seep out of the fissures, especially when subjected to heat or pressure. Others may oxidize over time so it becomes important for sellers to be able to offer services to clean and re-treat an emerald if so required.

Collector Quality

Deeply colored, large, relatively clean and non-treated emeralds are rare and collectible. There are also two rare kinds of unusual collector emeralds that are rarely seen commercially:

Cat’s eye – Green beryl that is saturated enough to be classified as emerald, and has microscopic hollow growth tubes that formed in a parallel fashion to one another throughout the gem. When cut en cabochon, the domed surface of these gems exhibits a rare cat’s eye phenomenon in direct (non-diffused) lighting.

Trapiche – These Colombian emeralds display a unique six-fold structure, (similar to spokes on a bicycle wheel) usually composed of a dark hexagonal central prism surrounded by six crystalographically-controlled prims separated by a mixture of albite and beryl containing either black carbonaceous shale (the host in which these emeralds form), or white albite (a form of feldspar) spokes. These gems are cut as slices or as cabochons to show the spokes radiating out from the centre. The name comes from the spokes in wheel-like sugar cane crushers, called trapiches, found in Colombia and other South American countries.

Localities

South America has been the world’s primary source for emerald since the discovery of the New World. The Incas traded emerald throughout their Andean empire until the arrival of Spanish Conquistadors. But the Spanish discovery of emerald in Colombia in the 1500s dramatically changed appreciation for the gem. Egypt’s and Austria’s emerald sources were quickly forgotten as European and Indian nobility demanded Colombia’s superb gems. This South American source quickly became the world’s most significant producer of fine emerald, and remains significant today. However, many other sources are gaining importance, including Brazil, Zambia, Zimbabwe, Ethiopia, India, Nigeria, Madagascar, Pakistan, Afghanistan, Russia and China. Emerald has been found on the North American continent as well; Hidden, North Carolina, is the U.S. historic emerald source, and some emerald material has also been discovered in the Yukon Territories, Canada. Neither location is commercially active, though rare collector gems are found from time to time.

Cutting, Care and Cleaning

Emerald is one of the few gemstones to have a specific cut named after it. The “emerald cut” is a square or rectangular outline step-cut with cut corners. Many emeralds are cut this way because it orients the gem to show its strongest color and the tapered corners prevent damage during setting. These cuts contain large table facets through which an admirer can best view the emerald’s rich color and its fascinating inclusion panorama. Emerald is increasingly cut in other shapes, including round, oval, free form, pear and marquise. It is important to closely examine all pointed corners for durability issues. It might be recommended for such gems to be mounted in earrings, pins or pendants (rather than rings) to minimize potential damage to sharp points. Emerald jewelry should not be cleaned in ultrasonic cleaning machines because the heat and vibration may damage or remove fillers. Emerald should not be immersed in detergents for similar reasons, and are best cleaned with a water-dampened, soft cloth. Common sense indicates it is not a good idea to wear an emerald ring during gardening or other intense physical activity.

Source: CIBJO Retailer Reference Guide, cibjo.org. Image: American Gem Trade Association