Emeralds are transparent gems formed from the mineral beryl, made green by trace elements of chromium, vanadium, and/or iron. Emerald is the birthstone for May, the most famous green gemstone, and one of the four precious stones alongside diamond, sapphire, and ruby.
To be called an emerald, a beryl gem must be primarily green, and possess a certain intensity of color. The most desirable stones fall in the bluish-green to pure green hue range, though yellowish-green stones are also valuable. Light green color gems are called green beryl, not emerald.
We’ve put together a list of the different types of emeralds you’re most likely to encounter being used in jewelry. As well as a few words of warning about certain stones that are sometimes described as emeralds, but aren’t actually emeralds.
1. Colombian Emeralds
Colombia has been a source of quality emeralds for well over a thousand years, with its highest quality gems famed for their vibrant, velvety deep green color. This is probably the color that comes into your mind when someone says “emerald green”.
Today, Colombia is the world’s largest emerald supplier. The finest emeralds, with vivid color saturation and high transparency, generally come from the Muzo and Coscuez mines. Chivor is also an important source, noted for producing emeralds with a bluish tint.
The Chalk Emerald and Mogul Mughal Emerald are among the most magnificent emeralds discovered in Colombia. Another is the flawless 18 carat weight Rockefeller Emerald, named for the business magnate that once owned it, which sold in 2017 for $5.5 million.
However, while Colombian mines deservedly have a reputation for excellence, keep in mind that every emerald-producing location yields both high and low quality gems. More important than origin is an emerald’s color, clarity and overall beauty.
2. Zambian Emeralds
Zambia is the second most important global producer of emeralds after Colombia, though its history of emerald mining is much shorter. Zambian emeralds were discovered in the 1920s, but it took until the 1970s for commercial mining to take off.
Among the top tier emeralds of Zambia and Colombia, there’s no major difference in quality. However, Colombian emeralds are usually priced higher than Zambian emeralds, due to having a few more centuries of historical significance and branding on their side.
A key characteristic of many Zambian emeralds is their higher iron content compared to emeralds from other sources. As a result, they can display bluish-green rather than pure green coloring, and tend to have fewer visible inclusions.
The major emerald mines in Zambia are located in the north-central Kafubu and Musakashi areas. In 2021, the Kagem mine in Kafubu revealed the world’s largest ever uncut emerald. Named Chipembele (a Bemba dialect word for “rhino”), it weighs 7,525 carats!
3. Brazilian Emeralds
Brazil is the third largest producer of emeralds. Brazilian emeralds tend to display less vibrancy and transparency than emeralds from Colombia and Zambia. Saying that, Brazil occasionally yields gems comparable to fine Colombian emeralds.
The two most important mining locations are Bahia and the Itabira-Ferros-Nova Era mining district of Minas Gerais. The Nova Era mine outputs some of the largest emeralds in the world, with stones known to reach sizes upwards of five pounds.
Most of the emeralds extracted in Brazil are not of gem quality. In Bahia, for instance, only about 1% of all mined material is suitable for faceting into gemstones for fine jewelry, with the rest being used for cabochons or carving.
Brazilian emerald colors span the full spectrum of green, from light and grassy to deep and verdant. As with Zambian emeralds, some Brazilian emeralds have high iron content, which can manifest in a darker or bluish-green appearance.
4. Cat’s Eye Emeralds
Some gemstones display chatoyancy, otherwise known as the cat’s eye effect. This optical phenomenon manifests as a narrow band of light across the surface of the stone. The effect resembles light bouncing off a cat’s eye, thus the name.
For chatoyancy to occur, a gemstone must contain a sufficient number of thin inclusions of a foreign mineral, often rutile or hematite, arranged in a parallel formation. It must also be cut into a cabochon, to allow light to reflect off of a rounded surface.
The cat’s eye effect appears in many gemstones, most commonly in quartz, and most strikingly in chrysoberyl. Chatoyancy also occurs in emeralds, but not often. This puts cat’s eye emeralds among the rarest emerald types.
Chatoyancy is more subtle in emeralds than in chrysoberyls – usually more of a thin pale line than a glowing white stripe. A cat’s eye emerald is considered particularly desirable if its band of light is straight, even, and prominent.
5. Untreated Emeralds
Emeralds are classified as Type III gemstones, meaning they almost always have noticeable inclusions. Most emeralds on the market have been treated to enhance their appearance and/or durability, usually via a treatment called “oiling”.
By soaking an emerald in cedar oil (or similar), the oil fills in some of the emerald’s internal fractures, reducing the visibility of these flaws. It can also improve the stone’s durability and color. This is why oiling is so widespread in the industry.
Untreated emeralds are extremely rare compared to treated emeralds. In fact, only about 0.5% of emeralds on the market are untreated, as most need treatment to make them strong enough to cut and polish, and attractive enough to sell.
An untreated emerald can fetch a significantly higher price than a treated one of similar quality. Untreated emeralds with naturally high clarity and vibrant color are the rarest of the rare, and more likely to be sold at auction than in a jewelry store.
6. Lab-Grown Emeralds
A lab-grown or synthetic emerald is chemically and optically identical to a natural emerald. The crucial difference that while natural emeralds are made inside the Earth, lab-grown emeralds are made by humans in a laboratory.
Another difference: because synthetic emerald manufacturers can control each stone’s mineral ingredients and growth process, a synthetic emerald will often display richer color and fewer inclusions than a natural one.
Lab-grown emeralds are more costly and difficult to create than some other synthetic gemstones like lab-grown sapphires and rubies. The synthesizing process is slower, and yields less high quality gem material.
Saying that, all types of synthetic gemstones are significantly less expensive than their natural counterparts. As such, a lab-grown emerald can present an attractive and more affordable option for your next piece of emerald jewelry.
7. Not Really Emeralds
The seventh and final entry on our list is an honorary mention encompassing several different stones that are sometimes described as emeralds, but actually aren’t.
There’s no such thing as blue color emeralds, since emeralds by definition must be green. “Blue emerald” is a misnomer occasionally given to aquamarine, a blue to blue-green beryl gem.
Again, yellow emeralds aren’t real because all true emeralds are green. You may encounter “yellow emerald” being inaccurately applied to yellow heliodor, a variety of beryl gemstone.
Red beryl is sometimes marketed as red or crimson emerald. Interestingly, though “red emerald” doesn’t exist, red beryls are many times rarer than true emeralds.
Demantoid garnets are green gems that can appear similar to emeralds. Russia is a major source for demantoids, which you may hear called “Uralian emeralds” for Russia’s Ural Mountains.
The term “African emerald” often refers to green fluorite, not to literal emeralds from Africa. Buyer beware: some green fluorite gems can strongly resemble genuine emeralds.
“Oriental emeralds” are actually green sapphires, typically sourced from Thailand or Sri Lanka. They tend to be pale olive green, lacking the verdant brightness of real emeralds.
A “Medina emerald” is an emerald simulant made from green glass. As Medina emeralds aren’t real gemstones, they’re used only in fashion and costume jewelry.