Emerald has been synonymous with the color green since ancient times. A fine emerald is a truly breathtaking sight, and this member of the beryl family deserves its placement among the traditional “Big Four” gems along with diamond, ruby, and sapphire.
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Top origins: Colombian emeralds command premium prices. Recent finds in Ethiopia may also command premium prices. Prices assume colorless clarity enhancement (no dyes). Average brilliancy of 40 to 60%. Add up to 20% or deduct to 10% for other cutting. Prices for emerald cuts, round, ovals and pear. Add to 10% for marquise.
Top Color: vstbG 5/5; bG 5/5 or 6/5; vslbG 5/5
Very Good Color: vstbG 6/5; bG 5/5, 4/5 or 6/4; vslbG 5/5, 6/5
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-ct Colombian stone as six times more valuable than three equivalent quality 1-ct 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 emeralds 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.
Sometimes green in SW; very seldom weak red, orange in LW. If red fluorescence is seen, the color is visible in the Chelsea filter. Fluorescence is quenched by Fe, as in the South African and Indian emeralds. See "Identifying Characteristics" below.
Fluorescent, UV-Long, UV-Short
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.
Emerald is a medium or darker green to blue-green beryl gemstone, in which the green color is derived from impurities of chromium (Cr), vanadium (V), or a combination of both. Before 1963, the definition of emerald was limited to beryls with chromium impurities, but the discovery in Brazil of a large deposit of beryl stones colored green by vanadium led to modification. According to the modern definition, the purity and saturation of the green color of a beryl is what defines an emerald.
Varying amounts of iron (Fe) will affect the color as well. More iron atoms increase the bluish tones.
In a situation similar to the division between pink sapphire and ruby, some chromium colored stones of light to medium-light green color are sometimes sold as emeralds though they could be considered green beryls. Emeralds should have a medium to dark primary green hue. (Editor’s note: Some gemologists, including Dr. Joel Arem, define emerald strictly as beryl that contains chromium and consider beryls colored green because of vanadium to be simply green beryls).
Do Emerald Colors Vary by Locality?
Geological conditions in Colombia produced exactly the slightly bluish-green shade and strong saturation that make stones from that locale the epitome of the variety.
Emeralds from the Muzo and Chivor mines in Colombia can be distinguished in a general way. Muzo material is yellowish green, whereas that from Chivor is blue-green. (It sometimes takes a trained eye to see the distinction in color, however).
Emeralds from Zambia may also display an unusual blue tone, with blue-green/yellow green pleochroism, due to their high iron content (0.73%). Zambian crystals may be intensely color zoned, with near colorless cores and dark green rims, almost like watermelon tourmaline.
Recently discovered emeralds from Itabira, Minas Gerais, Brazil, rival the best Colombian stones in quality. They are typically light bluish green down the c-axis.
Where are the Major Sources of Emeralds?
The center of world emerald mining is in South America, with Colombia and Brazil as major producers.
The Egyptian 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 locales typically produces a certain color, size, and clarity. Since 2016, Ethiopia has also produced some high-quality emeralds with grass green to blue-green colors that don’t need oil treatments.
Emeralds can feature many kinds of internal fractures and inclusions. The evocative term jardin, French for “garden,” is used to refer to this variety. The types of inclusions in emeralds can help identify their sources. See the tables below.
For inclusions of synthetic emeralds, see the “Synthetics” section below.
Inclusions: Oblong cavities parallel to long crystal axis, with gas bubbles; biotite crystals parallel to basal plane; fuchsite, 2-phase inclusions; apatite crystals; groups of negative twin crystals with comma shape.
Inclusions: Mossy inclusions; also interconnected tubes that make crystals appear turbid.
talc-quartz-carbonate enclosed in ultramafic
Inclusions: 2-phase inclusions; thin films; some liquid inclusions, few mineral crystals.
Inclusions (North Carolina): Quartz crystals sometimes seen.
Inclusions: Biotite (black crystals) as small specks or dots; pinpoints, breadcrumb inclusions; also tourmaline (dravite) and magnetite. Material from Kitwe contains: rutile, chrysoberyl, muscovite, apatite, quartz, ilmenite, tourmaline, color zoning, 2-phase inclusions.
Of course, other natural green gemstones may also resemble emeralds and may be misidentified — either accidentally or deliberately — as emeralds. Since emeralds are among the most popular and expensive gemstones in the world, unscrupulous vendors may associate the name “emerald” to other less popular green gems in order to drum up consumer interest, such as calling green fluorite “African emerald” or chrome sphene “Mexican emerald.” However, gemologists can usually readily distinguish emeralds from other gemstones.
If you’ve seen and priced synthetic emeralds, you may wonder why they’re so costly compared to other synthetics, such as synthetic sapphires. Both the hydrothermal and flux methods of production require costly equipment and are energy intensive. They take a long time to produce emeralds and have a low yield of cuttable gems.
Most emerald synthetics have the same absorption spectrum as natural emeralds. Gilson type III may have a line at 4270.
2.68-2.78 (usually over 2.69)
Flux-grown emerald doesn’t show the infrared spectrum characteristics of water in the beryl structure. This spectrum is characteristic only of natural and hydrothermal synthetic emeralds. Flux-grown emeralds typically have relatively low RIs and specific gravity values (SG) and show strong red fluorescence in UV.
Chlorine appears to be a diagnostic trace element found only in hydrothermal synthetics. Other trace elements overlap with natural material and are therefore not diagnostic. Natural emeralds contain Na, Mg, and Fe in significantly higher amounts (more than 0.1%) than synthetic emeralds but contain lower amounts (less than 18%) of silica and alumina.
Luminescence in Synthetic Emeralds
Chatham flux synthetic emerald: Weak to moderate red-brown and red, LW and SW.
Gilson flux synthetic emerald: Usually weak to moderate red, stronger in LW, some weak to moderate yellow, yellow green, or orange, LW and SW. Dull red in X-ray.
Gilson type III synthetic emerald: Inert.
Zerfass: Weak red in LW.
Regency (Linde): Bright red in LW.
Crystal Research: Inert.
Lenix: Red in LW.
Seiko: Green (distinctive) in LW.
Russian synthetic emerald: Weak to moderate orangish red LW, inert SW.
Hydrothermal synthetic emerald: Moderate to strong red, LW and SW, some inert.
Chatham stones transmit UV to 2300, whereas natural emeralds are opaque below 3000.
Regency emerald is the material formerly made by Linde, manufactured under license by Vacuum Ventures, Inc. This material is therefore identical with the Linde product.
Some of the first lab-created emeralds on the market weren’t convincing because they were so clean. However, the sophistication of today’s consumer has led to a trend toward more natural-looking synthetics with inclusions. Although this improves their salability, it makes a little more difficult for gemologists and appraisers to prove natural origin. Fortunately, the types of inclusions in synthetic emeralds can help gemologists verify either a mined or synthetic origin.
Flux grown synthetic emeralds may contain flux, platinum crystals, (metallic) phenakite crystals (colorless and low relief) and show a Venetian blind effect.
Lechleitner: Parallel color bands; dust-like particles; wedge-shaped 2-phase inclusions parallel to growth direction; octagonal gold crystals.
Biron: Fingerprints; veils; fractures; nail heads with liquid and gas; large 2-phase inclusions; white comet tails; gold particles; phenakite; growth features.
Crystal Research: 2-phase inclusions; color banding (in early material).
Inamori: 2-phase inclusions.
Tabulated Data on Synthetic Emerald
Lechleitner emerald has a Cr content of approximately 4-10% (weight), with mean RI varying from 1.576-1.605 as the Cr content increases. In contrast, Linde emerald has a Cr content of 0.3-1.2% and a mean RI of 1.568-1.575. Natural emeralds usually have a maximum Cr content below 2%, but the RI also varies with other impurities.
The properties of Seiko (flux-melt) emeralds are reported as similar to those of other synthetics.
Emerald is considered a “Type III” gemstone, which means these gems are virtually always included to some degree. Because of this designation, a clarity grade of “Very Slightly Included” is the normal range for emeralds. Well over 90% of the emeralds in commerce have been treated to minimize the appearance of the inclusions.
Emerald inclusions pose more than aesthetic considerations, however. Although emeralds, like other beryls, have a high hardness rating, they’re more fragile than other beryls. (A high Mohs rating doesn’t mean a stone is indestructible. It simply means the stone is more resistant to scratching). Their inclusions reduce their structural integrity, and these inclusions occur because of how emeralds form under the Earth. They’re unavoidable. Emerald enthusiasts will simply have to treat these gems gently.
The standard industry practice for enhancing emeralds 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.
Emerald is notorious for growing very large. The largest emerald crystal extant weighs 16,020 carats and is from the Muzo Mine in Colombia. (The “Bahia Emerald,” discovered in 2001, may take that title). Many museums around the world display fine and large emeralds, both rough and faceted gems, as well as some carvings and tumble-polished stones.
Smithsonian Institution (Washington, D.C): 117 (green, Colombia); 10.6 (North Carolina); 4.6 (green catseye, Colombia); 858-ct crystal, “the Gachalá.”
Moscow: 136 (nearly flawless, deep blue-green, step cut) (in the Diamond Fund).
Topkapi Museum, Istanbul: 6 cm hexagonal crystal; fine 8 cm crystal; 3 other large crystals.
Banque Markazi, Teheran: Many cabochons between 100 and 300 carats; one is 175 carats, another 225. There are also faceted gems of 100 and 110 carats; unmounted cabochons of 320, 303, 144.4, and two others over 250 carats.
British Museum of Natural History (London): “Devonshire Emerald,” a crystal 51 mm. long, weighs 1384 carats, fine color.
American Museum of Natural History (New York): Crystal 1200 carats, fine color, the “Patricia Emerald;” 630-ct crystal, “the St. Patrick Emerald.”
Banco de la Republica, Bogota, Colombia: collection of superb crystals from 220 to 1796 carats.
Private Collection: the “Atahuallpa Emerald,” 45 carats, set in the “Crown of the Andes,” a magnificent gold headpiece with 453 emeralds totaling 1521 carats. The Emilia crystal from Las Cruces Mine (near Gachalá) weighs 7025 carats.
Keep in mind that sometimes the following names are used to refer to emeralds from these specific sources. However, they may also be used as trade names to describe emeralds with particular characteristics, regardless of source. If you’re not sure how vendors are using the term, ask them for clarification.
Vivid, slightly bluish green stones of medium to medium-dark color are often called “Colombian emeralds” no matter what their actual geographic origin.
Emeralds of lighter color are sometimes called “Brazilian,” even if they were mined in Africa.
Emeralds less blue and less saturated than Colombians but more included are sometimes called “Russian” or “Siberian,” whether or not they’re from Russia.
Small, highly included emeralds with deep color are sometimes called “Sandawana,” even if they’re not from this Zimbabwe locale.
Emeralds that tend towards gray are sometimes called “Zambian.”
Emerald rings should have protective settings to shield the gem from physical blows. Emeralds also make excellent choices for pendants, brooches, and earrings.
Mechanical cleaning is not recommended for emeralds. In the worst case, ultrasonic, steam, and boiling methods can shatter emeralds. At the very least, these methods will mean you’ll have to re-oil your emerald. Use only warm water, detergent, and soft brush for cleaning or take your emeralds to a professional jeweler.