A Consumer’s Guide to Emerald Treatments

emerald treatments - ring
“Old Emerald Ring” by Alden Chadwick. Licensed under CC By 2.0.

People often ask me, “Are all emeralds treated?” Simple answer: no. Not all. However, the vast majority do receive treatments. Just like sapphires and heating, assume emerald gems are treated until proven otherwise.

There are many treatments and enhancements regularly applied to emeralds. Personally, I don’t have any problems with people treating gemstones and selling them in the trade, as long as they disclose the treatments. Nevertheless, some of these emerald treatments are very questionable and I don’t recommend them. Of course, others have no issues with them, especially emerald dealers.

I’m going to share my opinions of these practices with you. As consumers, you’ll have to decide for yourselves whether you want to purchase treated emeralds.

Oil Treatments

Oiling gemstones to fill internal fractures is a common practice. Many different oils are used for emerald fractures. For example, using colorless cedarwood oil is a supposedly acceptable practice. Colored oils are also used.

I have definite issues with oiling gemstones. Although many others in the trade will tell you it’s fine, I don’t consider this an acceptable practice. I would advise against buying any oiled gemstones.

Why do I say this?

  • Oil hides flaws and improves colors. Of course, this is why the treatment is done in the first place. However, these concealed flaws could make the stone more fragile than it appears. It may even be unsuitable for jewelry use.
  • Most likely, the emerald dealers won’t tell you how much the stone’s improved. Why? Because they can’t. Oiling often takes place long before dealers and vendors acquire the stone. Assuming they’re honest, they just plain don’t know.
  • Due to the oil, you can’t really tell the quality of the stone. This is usually to the buyer’s loss.
  • Sooner or later, oils will wear off (and out of) emeralds. In other words, the “improvement” isn’t permanent. When it wears off, your stone will probably look terrible.
  • Keep in mind that emerald jewelry, in particular, suffers a lot of wear and tear. (Emeralds usually don’t wear well precisely because of their flaws). If you need to fix a crack, chip, or do any re-cutting, oiling will present problems. The fresh cuts (fixed facets) usually won’t match the rest of the stone. In addition, you’ll need the stone re-oiled to make it look decent again. This takes time and money. Many cutters (myself included) won’t even consider re-cutting an expensive emerald due to the problems and liability involved.

Consider some alternative gems (see below) instead of buying any oiled stones.

Oiling Versus Heating

I’ve heard some dealers compare oiling emeralds to heating sapphires. They argue that both practices are essentially the same. That’s not true. Heating sapphires produces basically permanent colors. Furthermore, heating also occurs in nature. (However, artificial heat treatments, after mining, should still be disclosed). Have you ever heard of stones coming out of the ground already oiled?

To be clear, when shopping for gems, always assume both emeralds and sapphires receive treatments. Don’t assume the treatments have the same impact on the gems’ value and durability.

Opticon Filler

Opticon is a plastic polymer resin. It’s injected onto and into emeralds, both rough and cut, often under a vacuum. Although this treatment has more stability than oiling, it will yellow and disintegrate with age and some solvents. It fills flaws and helps improve color and some durability. (Again, that’s why people use it).

If dealers disclose this treatment and lower the emerald price, I’m more neutral on the use of Opticon. However, even after an Opticon treatment, emeralds often still get oiled. I haven’t changed my opinion on that.

As long as dealers disclose emerald treatments and value treated stones lower than untreated, quality emeralds, I’m inclined to neutrality. Do quality, untreated natural emeralds actually exist? That brings us to the next topic to consider.

Do You Want a Flawed but Improved Gem?

The only natural emeralds I’ve ever seen that I thought were pretty nice when untreated hailed from Zambia. However, I haven’t seen a lot of those. Also, keep in mind that Zambian material can (and often does) receive oiling. I should disclose that I probably couldn’t afford the ones I did like. To be honest, I didn’t want to pay the offered price when I considered what other stones I could buy with the money.

Most all of the natural Colombian material I’ve seen hasn’t been particularly good. It has lots of flaws and inclusions. That’s just my experience. You might find some good ones.

Again, emerald treatments exist in the first place to improve these gems. Ask yourself, do you really want a flawed stone that’s been “improved?” If so, how much improvement is OK? Where does it stop?

emerald treatments - Colombia
“Emeralds4960,” apparently water-worn crystal pebbles, from Colombia, by Bob Richmond. Licensed under CC By 2.0.

Emeralds and Flaws

The GIA system for clarity grading separates stone types into different categories, Types I, II, and III. These categories reflect the likelihood that the stones possess inclusions, based on their formation. Type I gems usually have no eye visible inclusions. Type IIs usually possess inclusions, while Type IIIs almost always do. (Emerald belongs in the Type III category). Although the stones can receive the same clarity grades, the grades have different meanings based on the stone category.

This GIA model holds that you can’t compare all gemstones to each other. We should grade like gemstones to like gemstones.

I don’t agree with this grading system.

Sorry guys, a dirty stone (flawed or included) is a dirty stone. I don’t care if they’re emeralds and it’s accepted practice to call them good quality. (Emeralds can get the highest clarity grade, “VVS,” but what that means for Type III gems differs from what that means for Type I gems).

I realize saying “They’re really flawed” would impact the sale of emeralds and other gems. That’s my point. I know emeralds don’t occur clean and flawless naturally. What we consider a good emerald, in terms of clarity, will still have inclusions. There’s nothing wrong with that. My point is they’re included. I don’t believe we should have separate clarity categories for emeralds or other stones. They’ll still be worth what they’re worth because they’re emeralds (or whatever) and that’s how they occur in nature.

Comparing an Emerald and an Aquamarine with the Same Clarity Grade

In my opinion, having different clarity standards for different gemstones in the GIA system is confusing. That’s the main problem.

For example, take an aquamarine (also a member of the beryl family, like emerald). Say you find it has a clarity grade of “VS” (very small inclusions) and it’s really quite clean. You probably won’t see anything with your naked eye unless you have a lot of training.

Now, let’s say you find an emerald also graded “VS.” It has the same grade as the aquamarine you just considered. How do they actually compare, in terms of clarity?

It turns out that in the GIA system, aquamarine falls into category Type I. For these gems, a grade of VS means it has minor inclusions, somewhat easy to see with 10X loupe. Emeralds, on the other hand, are Type III gems. For emeralds, a VS score means its inclusions are obvious under 10X. This stone, compared to an aquamarine with the same grade, would actually appear pretty included.

Confused yet?

The GIA categories and grades in combination do describe the stones truthfully. However, as consumers, you’ll need to read the fine print and understand the system. Very few people outside of the gem business do. Of course, this information isn’t withheld from the public. You can certainly find it. Just do your research.

emerald treatments - Brazil
“Opaque Emeralds from Brazil” by Mauro Cateb. Licensed under CC By 2.0.

An Alternative Clarity Grading System

Why not always make clarity grading consistent for all types of stones? For the stones I cut, I use my own common sense gemstone grading system for both clarity and color. It has a set of grades, each with a single meaning, for use on all gems, regardless of “type.” Of course, I also have stones certified by GIA gemologists with GIA clarity grades. I work with these at the requests of customers or jewelers with whom I do business.

Gemstone Alternatives to Treated Emeralds

Just to clarify, if you’re getting the idea I don’t recommend buying emeralds, treated or otherwise, you’re correct. In my opinion, you can buy other, better quality gemstones for the same money. Shop around and you’ll find some nice green-colored alternatives better suited for jewelry and actually worth what you’ll pay. Sorry, emerald fans. I very seldom see emeralds from anywhere worth the money.

Synthetic Emeralds

Personally, I don’t like cutting synthetic rough. However, if you really want to cut emeralds, choose hydrothermally grown synthetic emeralds. Truthfully, they make good replacements, especially when you consider all the dyes, oils, and other emerald treatments natural emeralds receive.

I can just hear people saying, “No, give me the dyed, plastic-injected natural gems instead of the lab-grown stuff.”


Green garnets from Tanzania, tsavorites don’t get very large. The trade would consider a 5-carat cut stone very large, while 1-carat stones are fairly common. However, their color rivals emerald’s, and you can usually find them clean, rough or cut. Usually, they receive no treatments. Also, these gems can match or exceed emeralds in hardness. Since they typically have few inclusions and no cleavage, they’re more durable jewelry stones than emeralds. Pricewise, tsavorites fall in the same range, more or less, as emeralds, depending on the market. However, they also have a dispersion and brilliance emeralds can’t match.

alternative to emerald treatments - tsavorite
“Tsavorite Garnet,” 0.86 cts, freeform cut, 4.1 mm x 5.3 mm, rich medium dark green. © Dan Stair Custom Gemstones. Used with permission.

Mint Grossular Garnet

Merelani mint garnets are one of my favorites. Typically, you won’t find these grossular garnets in large sizes. However, rough that will cut a clean, 1-carat gem is fairly common. Although this mint green isn’t as dark as a lot of emerald colors, I think it’s very pretty. Some stones can match emerald’s hardness, and have a lot of sparkle. These gems don’t usually receive treatments.

Chrome Tourmaline

Harder and more durable than emerald, you’ll find chrome tourmaline, rough or cut, more easily and for less money than tsavorite and emerald. If you’re buying rough, watch the color. This tourmaline variety can have very intense saturation, which might make for a very dark green gem. Be aware of the difference between chrome tourmalines and green tourmalines or verdelites (see below). Unscrupulous vendors might offer green tourmalines as the more expensive chrome variety.

Green Tourmaline

I’ve seen a fair amount of green tourmaline material that, while not exactly the chrome color of emeralds, comes very close or better, in my opinion. Material from Afghanistan in particular is gorgeous and very reasonable moneywise when compared to emeralds.

Chrome Diopside

The green chrome variety of diopside has a lower hardness than emerald and a refractive index (RI) of 1.67-1.72. For jewelry applications like rings, it’s just not hard enough. However, it should work fine for earrings and pendants. In small sizes (1 to 2 gram material), you can find it easily and inexpensively. Be aware that larger stones tend to be darker in color. These gems usually receive no treatments.


I know what most people think. Emerald and peridot show different shades of green. Nevertheless, I’ve seen peridots with emerald color and a sparkle (1.69 RI and a very high dispersion) that no emeralds could ever match. While not common, I’ve cut this material. These gems usually receive no treatments.


If you still want to buy an emerald, I wish you good luck. However, a little education about emerald treatments and alternatives will also serve you well. Be aware of how the GIA clarity grades work. I hope I’ve educated (or scared) you a bit. At least, you’ve now heard from someone with a different point of view.

alternative to emerald treatments - chrome diopside
“1.00-Ct Round 5mm Green Chrome Diopside 925 Sterling Silver Stud Earrings” by Jerry Juniot. Licensed under CC By-SA 2.0.
Gram Faceting Archive of Information
This edited version of an article by the late Jeff Graham is part of a special archived informational series from Gram Faceting. Used with permission.