Emerald Buying Guide


old mine emerald in a modern ring - emerald buying guide
A modern ring featuring a Colombian old mine Muzo emerald with insignificant treatment (center) and two emeralds sourced to match. © Jogani Beverly Hills. Used with permission.

The celebrated emerald of lore, the May birthstone, has a place in any gem collection. However, it poses some challenges. Although one of the three primary color gems (along with ruby and sapphire), the emerald has an entirely different market than other gems. Even very high quality emeralds have flaws and inclusions. As a result, green gems of all sorts, such as sapphire, diopside, peridot, fluorite, tourmaline, and more, have been used as simulants. They’ve also received marketable but misleading names like “oriental emerald” to increase their value.

Indeed, if green jewelry is your ultimate goal, you may find a natural emerald the most expensive option for the quality of the gem.

Emerald Buying and the 4Cs

The IGS emerald value listing has price guidelines for faceted and cabbed pieces.

Color

How Green is Emerald Green?

As with other colored gems, the primary factor in an emerald’s value is its color. Emerald is the green variety of beryl, and its color arises from trace amounts of chromium or vanadium. Trace iron content may cause secondary blue or yellow hues.

Chromium or Vanadium?

Some connoisseurs assert that true emeralds are colored by chromium, and the gems colored primarily with vanadium are simply green beryl.  The distinction coincides with the emerald’s geologic origin. Chromium colors Colombian stones, generally the most expensive. They will show red under a Chelsea filter. On the other hand, vanadium primarily colors Brazilian and Zambian emeralds.

Blue Hues

Gems with secondary blue hues (10-15%) are the most highly prized. Blue hues can make the gem appear richer and warmer, but emeralds with more than 15% secondary blue hues are considered “overblue” and may appear blue under incandescent light. Colombian emeralds often exhibit secondary blue hues, and many connoisseurs consider these gems the epitome of emerald green.

Brazilian emerald pendant - emerald buying guide
Brazilian emerald pendant with secondary blue hues. © Bear Williams, Stone Group Labs. Used with permission.
Yellow Hues

Emeralds can also show secondary yellow hues (10-15%). Such gems are less highly coveted. However, some collectors consider the yellow a “balance” against the blue of incandescent light and, thus, prefer yellow-hued emeralds (Wise, 2016).

lab-created emerald ring - emerald buying guide
Lab-created emerald ring with secondary yellow hues. © CustomMade. Used with permission
Color Variations and Value

Slight variations in hue can significantly alter price.  A gem with slight blue hues may sell for twice the price of a similar quality gem with yellow hues. Photos simply can’t easily capture the nuances of hue. (Unfortunately, this makes emerald online marketplaces especially difficult to navigate). You can view these nuances best in person.

Emerald tone and saturation also play key roles in the aesthetics and value of a gem. Natural emeralds exhibit a wide range of tones, from very light to very dark, with medium-dark tones around 75% the most valued. Saturation can vary from dull to vivid and greatly impacts the emerald’s quality.

clarity variations - emerald buying guide
“Colombian emeralds” by Mauro Cateb. Licensed under CC By 2.0.

High-quality emeralds will have no visible zoning in hue, tone, or saturation. Some emeralds receive color enhancing treatments. However, stones with these impermanent enhancements will lose color or yellow over time.

Clarity

The Gemological Institute of America (GIA) clarity grading system treats emerald as a “Type III” gemstone. This means that eye clean emeralds are extremely rare. As a result, a large quantity of flaws and inclusions are tolerated.

The Jardin

Due to the resemblance of this gem’s inner landscape to roots and stems, aficionados use the term jardin, French for garden, to refer to an emerald’s inclusions.

Zambian emerald inclusions - emerald buying guide
Close-up view of Zambian emerald jardin.

A jardin can vary greatly from one emerald to another. Those gems with fewer inclusions receive higher values. Colorless inclusions are preferred to colored or black inclusions. Flaws on the gem’s surface are undesirable, since they may cause cracks and decrease the emerald’s wearability.

light and dark jardin elements - emerald buying guide
1.83-carat Brazilian emerald featuring both light and dark jardin elements. © Bear Williams, Stone Group Labs. Used with permission.
Clarity Enhancement

Due to inclusions and fractures, most emeralds have received treatments to improve their appearance. As a result, the GIA devised a scale to classify an emerald’s clarity enhancements. These may rank as minor, moderate, or significant. This factor will affect the emerald’s care. A stone that has undergone significant enhancement will lose some clarity over time. Thus,  gem owners may need to have oils and resins reapplied to their emeralds.

Cut

The emerald cut is a classic for a reason. This gem cutting design enhances the crystal’s natural color while minimizing wasted rough.

An emerald with a light tone may take a deeper cut with fewer facets to enhance the color. Likewise, a very dark specimen may take a more shallow cut or more facets to lighten it.

classic emerald-cut emerald - emerald buying guide
1.18-carat Colombian emerald with classic emerald cut. © Bear Williams, Stone Group Labs. Used with permission.

Some faceters cut emeralds into rounds or ovals. However, these shapes require cutting away more rough material. While brilliant-cut emeralds scintillate more than emerald-cut stones, they will lose the satiny texture the traditional cut brings out (Wise, 2016).

brilliant-cut synthetic emerald ring - emerald buying guide
Brilliant-cut lab-created emerald in a ring. © CustomMade. Used with permission.

Cabochons cost less than faceted gems but can also bring out an emerald’s  inner beauty.

emerald cabochons - emerald buying guide
27.31-carat Colombian emerald cabochons. © Bear Williams, Stone Group Labs. Used with permission.

Carat

Like many gems, emerald price per carat increases markedly with size.  Still, the price depends more on the stone’s quality, with the most exceptional gems commanding 5 to 10 times more per carat than those of lesser quality.

Emerald Buying Caveats

You may find many green gemstones advertised as emeralds. For example, be aware that so-called “oriental emeralds” are actually green sapphires. Real, natural emeralds won’t have descriptive qualifiers in their names. Due to the pervasiveness of imitations, you should obtain a certificate for your emerald from an independent gemological laboratory.

However, also remember that many natural emeralds receive treatments to enhance clarity and color.

Treated Emeralds

You should know what treatments your emeralds have received so you can care for them properly. Most such treatments will deteriorate over time, becoming cloudy or wearing off the stone.

These enhancements generally involve filling cracks and fissures with oil, resin, or a polymer.  These treatments will need to be reapplied to maintain the visual quality of the gem.

Dyed oils or fillers and chromium powder treatments may have been used to enhance the color of a pale gem or even out the tone in a gem with color zoning.  These treatments may lose color over time and require treatment.

Synthetic Emeralds

Lab-grown emeralds, chemically indistinct from natural emeralds, offer much better quality for the price. With far fewer inclusions and flaws, these don’t require treatment to increase clarity and are less susceptible to cracking. Some consumers may prefer lab-made emeralds, such as those in the CustomMade rings shown here, for their eye clean clarity or for ethical reasons.  These qualities make them ideal substitutes for natural emeralds in jewelry.

Jewelry Considerations for Emerald Buying

Care and Repair

An emerald’s jardin gives it a unique character but also makes it brittle and subject to cracking. Maintaining an emerald in a jewelry piece requires proper care.

Furthermore, chips or cracks in the stone can be difficult to repair. Some gem cutters refuse to repair emeralds because of the difficulties involved.  However, experienced lapidaries have successfully recut damaged stones into beautiful pieces.

before and after recut - emerald buying guide
Colombian emerald, 8.81-ct (left), recut to 7.67-ct (right) and enhanced with ExCel by the Clarity Enhancement Laboratory. Recutting the stone greatly improved transparency and color, and the AGL Prestige Report notes that the stone underwent minor enhancement. © Mardon Jewelers. Used with permission.

Rough Emerald

To profit from cutting rough emerald, carefully consider the crystal in terms of weight retention and inclusion management. (Be especially aware of what inclusions may remain on the surface). Often, you must cut away 80-90% of the rough for a jewelry piece. Without years of experience, determining the final state from the rough stone will be difficult.

emerald rough - emerald buying guide
Rough Colombian emerald (8.23-ct). © Bear Williams, Stone Group Labs. Used with permission.

Old Mine Gems

You’ll find some emeralds referred to as “old mine” gems. This terminology is used sometimes to refer to old gems and other times to describe a very fine emerald with a transparency almost like honey or clear oil. Emerald connoisseurs seek out gems with this softening effect, caused by transparent hexagonal growth structures. Other terms for this prized quality include “drop of oil” (gota de aceite), “butterfly wing” (efecto aleta de mariposa), or snigda (Sanskrit for smooth) (Wise, 2016).

old mine emerald - emerald buying guide
Very fine old mine Muzo emerald with no enhancement in antique platinum setting. Photo: Jeff Scovil. Cora N. Miller Collection, Yale Peabody Museum of Natural History. Courtesy R. W. Wise, Goldsmiths, from Secrets of the Gem Trade. Used with permission.

Trapiche and Cat’s Eye Emeralds

Occasionally, black carbon inclusions form along the six-sided growth pattern of the beryl crystal, creating a six-pointed pattern.  Called a trapiche after the term used in Colombia for a grinding wheel, these gems are extremely rare. A quality trapiche emerald will command a high price.  These stones sometimes exhibit a chatoyant or “cat’s eye” effect and can receive cuts to showcase this feature.

cat's eye trapiche emerald - emerald buying guide
“Trapiche emerald with cat’s eye effect in segments.” Photo by Jeff Scovil, © Primagem. Used with permission.

References

Wise, R. W. (2016). Secrets of the Gem Trade: The Connoisseur’s Guide to Precious Gemstones (2nd ed.). Lenox, MA: Brunswick House Press.