Emeralds are a variety of the mineral beryl that is colored green by trace amounts of chromium and sometimes vanadium. Real emeralds are some of the most valuable and desired gemstones due to their beautiful green color and rarity. But what exactly determines the color of a real emerald?
What Makes Emeralds Green
The green color of emeralds is caused by small amounts of chromium and/or vanadium within the crystal structure of beryl. These trace elements cause the absorption of yellow and blue light, resulting in the characteristic green colors of emerald. The more chromium and/or vanadium, the deeper and more intense the green color. Emeralds without these trace elements would simply be colorless beryl.
The amount of chromium in an emerald can range from 0.1% to 1.5% by weight. Rarer still are emeralds colored by vanadium, which can comprise 0.1% to 2% of the stone’s weight. Many emeralds actually contain a combination of both chromium and vanadium as the coloring agents.
Hue, Tone, and Saturation
The exact green color of an emerald depends on three attributes:
- Hue – The actual shade of green, ranging from yellow-green to blue-green.
- Tone – How light or dark the color is.
- Saturation – The intensity or purity of the color.
By varying these three parameters, emeralds can display a wide spectrum of green shades and depths. Here are some of the primary emerald colors:
| Emerald Color | Description |
|---|---|
| Green Yellow | Hue is more towards yellow, lighter tone, lower saturation. Often found in Colombian emeralds. |
| Pure Green | Balanced hue, vivid saturation. Classic emerald shade. |
| Bluish Green | Hue skews towards blue, deeper tone, high saturation. More common in emeralds from Zambia. |
The geological conditions in which the emerald formed dictate these color characteristics. The amount of chromium or vanadium present, other trace elements, lattice defects in the crystal – all affect the final color that is visible.
Clarity
Like other gemstones, the clarity of an emerald also influences its appearance. Inclusions, fractures, and other imperfections in the crystal can impact the observed color. For example, murky or heavily included emeralds will often appear darker in tone compared to cleaner stones.
Emeralds typically have more inclusions than other gems like diamonds. However, a stone with too many or too large inclusions would be considered less desirable. Finding emeralds with minimal flaws and high clarity is rare, especially for larger gemstones.
Cut Quality
How well an emerald is cut also affects the vibrancy of its color. The principles of cutting emeralds involves maximizing the hue and saturation while minimizing any discoloration from inclusions. Proper cutting requires immense skill to optimize the color refraction and appearance.
An exquisitely cut emerald will fully display its most vivid green while downplaying any visible flaws. On the other hand, a poorly cut stone may exhibit muddled, lackluster color even with minimal inclusions. The cut quality can mean the difference between dull and dazzling.
Effects of Lighting
The lighting conditions when viewing an emerald also influence the perceived color. This photo-effect of emeralds can make them appear slightly different colors in various lighting setups.
In daylight conditions, emeralds exhibit their most accurate green color. But under incandescent bulbs or candlelight, the yellowness of the light source brings out more yellowy-greens. In shaded lighting, emeralds may take on deeper, more bluish-green hues. Careful observation under standardized lighting is needed to fully evaluate emerald color objectively.
Green Dyes and Treatments
Unfortunately, there are ways unscrupulous sellers may enhance or alter the color of emeralds artificially. Green-tinted oil, epoxy resins, or other polymers can be used to fill fractures and improve the apparent color.
While this is allowed with disclosure, excessive dyeing to mask flaws or change color is considered deceptive. True connoisseurs value emeralds with natural, unaltered color over heavily treated stones.
Evaluating Emerald Color
Judging emerald color requires an understanding of hue, tone, and saturation along with effects of clarity and cutting quality. But there are still subjective preferences in color beauty. Some prize a pure, vivid green while others favor nuanced bluish-greens.
Here are some general guidelines used by jewelers and gemologists when evaluating emerald color:
- Hue should be moderately bluish-green to pure green, not yellowish-green.
- Tone should not be overly dark or excessively light.
- Saturation should be sufficiently vivid but not garish.
- Color zoning should be minimal across the stone.
- Secondary colors like yellow, brown, or gray are undesirable.
With parcel emeralds of otherwise equivalent size and clarity, those with the most pleasing, intense greens command the highest prices per carat.
Famous Emeralds by Color
Some of the world’s most famous emeralds provide excellent examples of prized green colors.
- Patricia Emerald – A flawless 632 carat Colombian emerald exhibiting a vivid bluish-green hue.
- Chalk Emerald – One of the largest gem-quality emeralds at 37.8 carats, with a rich green color.
- Duke of Devonshire Emerald – Historically significant Colombian emerald with desirable pure green color.
- Rockefeller Emerald – Superb 18.04 carat emerald from Colombia with highly saturated green.
Emeralds from classic sources like Colombia and Zambia are prized for their bluish-green and green colors respectively. But beautiful emeralds can originate anywhere if conditions produce the right trace elements for vivid green color.
Identifying Fake Emeralds
Synthetic and imitation emeralds are common so buyers must beware. Man-made gems like cubic zirconia may resemble emerald but are much softer or lack distinct crystal structures under magnification.
Lab-grown emeralds have essentially identical physical and chemical properties compared to natural emeralds. Advanced testing is required to confirm if an emerald is synthetic or not.
Other tricks like green-colored glass passed off as emerald are easier to identify. Look for bubble inclusions, uniform saturation, colored flashes from facet junctions, and softness indicating glass.
Conclusion
A beautiful emerald requires the perfect combination of light to medium green hue, sufficient saturation, even color distribution, high clarity, and excellent cut. While personal taste plays a role, jewelers universally prize emeralds with a vivid pure green free of distracting secondary colors.
Colombian emeralds remain the historic standard, but sources in Brazil, Zambia, Ethiopia, and Russia also produce top quality emeralds in various shades of green. Ultimately an emerald’s beauty stems from how well it balances color, clarity, and brilliance.