Emerald Treatment Guide – No Oil, Minor, Moderate and Significant Treatment Emeralds

Emerald Treatment Video

A video explanation of different emerald qualities is shown below:


Before buying any emerald it is important to know what type of treatment it has gone through.

Emerald has different levels of treatment.

  • Natural (No Oil or No Treatment)
  • Minor, Moderate, Significant Treatment – This includes oil, resin, and dye

The price is dependant on the level of treatment and/or type of treatment the emerald went through.  Price can range from exceptionally expensive US$10,000+ per carat for no oil emeralds to US$10 per carat for aggressively treated emeralds.


An exceptionally high-quality emerald above the 5-carat size that is untreated could fetch prices above US$50,000 per carat!

One example happened a decade ago on May 29th, 2012 in Christie’s Spring Hong Kong auction.  They sold a “7.05ct Colombia, no oil rectangular-cut emerald and 9.04ct E VVS2 rectangular-cut diamond ring” for a realized price of HK$8,420,000(US$1,090,080).

Assuming both diamond and emerald prices were split 50/50, the emerald would have cost around US$500,000 or over US$70,000 per carat!

However, lower quality emeralds that have been “significantly” treated with oil, dye, and resin can fetch prices of around US$10 per carat!


You can save thousands of dollars by checking the authenticity of the certificate and understanding the ‘treatment’ section.  Also, it will save you time and the harassment of getting scammed by the seller as they did not inform you.

I hope this guide will provide you with a basic understanding of the different types of emerald treatments.

I do want to emphasize that even if you have read this guide completely and understood the basics.  It does take years of experience looking at emeralds to understand the different levels of treatments.

If there is any doubt about your purchase – “Even that slight 1% chance” – it is always best to verify the stone from a reliable gemstone laboratory or trustworthy gem dealer.


Almost all emeralds are treated with filler substances like oil, resin, or a combination of multiple substances.

The trade estimates that more than 99 percent of emeralds have some treatments.  In terms of the Mohs scale of hardness, emeralds are relatively hard (7.5 to 8.0 range).   But they are softer when compared with the other big three gemstones – rubies, sapphires, and diamonds.

However, almost all emeralds have some natural inclusions or fractures in them.

This is because the emerald crystals were naturally formed that way.  Plus the harsh mining techniques do not help either.

That is why GIA classify emeralds as Type III gemstones.   Gemstones which are “naturally included.”  So, please do not run, if you see an emerald with inclusions.


How emeralds are mined, transported, and cut does not help.  It is the biggest reason why almost all have been subject to some treatment.

When rough emeralds are mined, almost “all” are immediately thrown into a barrel of oil.   When cutting them, the cutter will keep oil to lubricate them.

Finally, when the trader or wholesaler wants to sell it, they will soak the emeralds again in oil or other substances.

The treatments they will use include

  1. The colorless kind, which is accepted in the trade.
  2. Enhanced color oil, which is not accepted.
  3. Resin, which is almost impossible to remove.

All these treatments are used to improve the stone’s clarity.   With these treatments, the emerald can “command” a higher price than the original untreated state as it looks more attractive.

So, now you know why almost all emeralds are treated!

Also, once an emerald is purchased, you should also be careful in sending it to a jeweler who uses ultrasonic or steam to clean your ring.  Ultrasonic vibrations can weaken the emeralds which are already fractured.

The hot steam can also cause oil or unhardened resin to sweat out of the surface-reaching fractures.  This will make the stone look unattractive and included again.

Therefore, gentle scrubbing with warm, soapy water is the safest way to clean emeralds.


Natural emeralds that are not treated are ‘rarest of rare’ gemstones.  And as read above can command astronomical prices!

So, how do you know if your emerald has no oil or resin in it?  It is actually very simple!

You just have to find an emerald that has no fractures on the surface, so no foreign substance can get inside it!  This will guarantee the emerald doesn’t have any treatment.

If the crystal is so clean or does not have surface-reaching fractures, there is no chance for any treatment to enter the stone.


To check for emerald fractures, you have to use natural gem daylight (tube light) or sunlight.

We then need to tilt the emerald at such an angle so that the light reflects from the surface of the stone.  The reflected surface will look “white” as shown in the image below.

Then using your microscope or gem loupe, you need to check if there are any dark lines or indented lines from the reflective surface.

If you do see these lines, then this indicates there are some fractures reaching the surface.

This almost guarantees (with 99% probability) that some foreign substance has entered inside the emerald.

Emerald Treatment - Area highlighted in yellow shows the reflective light look & the dark lines which proves this emerald has fractures reaching the surface.
The area highlighted in yellow shows the reflective light & the dark line. This proves this emerald has fractures reaching the surface. This emerald probably has foreign substance inside stone.

However, if you do not see anything in all the gem facets then you might have in front of you the rarest of rare gemstones!

Emerald treatment - Image of no oil emerald no surface reaching fracture
Emerald that has “no oil, resin or any foreign substance.” As there isn’t any fracture reaching the surface of the stone.

If you do come across an emerald that has no oil, no resin, or no treatments.  And has a clean, uncloudy crystal.  You should sit down and “savior” the sight because they are exceptionally rare.

Finding a replacement with these characteristics is almost impossible, even for dealers like us!

The emerald in the above image was so clean that GIA actually sent our stone for verification from Bangkok to Hong Kong as they couldn’t believe their own ‘eyes’ either.  They thought it was a ‘synthetic’ emerald!


Checking the different levels of treatments in emeralds is difficult.   It does require sophisticated equipment to tell what type of fillers are in an emerald.

As explained above, most emeralds are treated multiple times.  This means they will have a higher chance of different fillers inside them.

If you do have a microscope with darkfield illumination & fiber optic light, you can check the presence of filler by tilting the emerald back and forth.  By doing this tilting motion, both front and side view, we have to check for “visible color flashes.”

You should check for these flashes along the fissures that reached the surface of the emerald.  The process of finding these surface-reaching fissures was explained above section – “HOW TO CHECK FOR EMERALD FRACTURES?”

Filling substances flashes orange in this image. (Photo by: R.W. Hughes)
Filling substances flashes orange in this image. (Photo courtesy by: R.W. Hughes)

If you do see these flashes you will know the emerald has some foreign substance inside.  This will not specify the type of filler but will let you know that some filler is present.

Another way to detect filler presence is by checking the emerald under fluorescence light.  On some occasions, foreign material will fluoresce.  However, not all emeralds’ fillers flash or fluoresce, so both these tests are not 100% reliable.

Finally, once the above steps are done, trained gemologists will start to look for fillers inside the emerald under the microscope.

This skill requires some training and experience because telling the difference between fillers from natural liquid inclusions is difficult.

Descriptions of what to look for in both natural emeralds and fracture-filled emeralds are described below.

Natural Emerald Inclusions Are:

  • Liquid-filled inclusions
  • Fingerprints
  • Two-phase and three-phase inclusions
  • Angular growth zoning
  • Tube-like and needle-like inclusions
  • Mineral inclusions including pyrite crystals, calcite inclusions along with fractures, and biotite flakes

Fracture-Filled Emerald Inclusions Are:

  • Flash effect of various colors.  Like orange to pinkish-purple flash, blue flash, or yellow-orange to blue flash.
  • Oil might have a slightly yellowish or brownish color. Be careful not to confuse this color with oxide staining in fractures.
  • Decomposed oils might leave whitish or yellowish branch-like patterns
  • Might see trapped bubbles in the filling material, flow structure or whitish, textured cloudy areas.

    Gas bubble inclusion seen next to natural emerald inclusions. Proves filler substance inside the emerald. (Photo courtesy by: R.W. Hughes_
    Gas bubble inclusion is seen next to natural emerald inclusions. Proves filler substance inside the emerald. (Photo courtesy by: R.W. Hughes)


There was a study done by GIA in 1999, that explains how they classify emerald treatments as minor, moderate, or significant.

The easiest way to classify and standardize the different levels of treatments was to define these categories.   GIA decided to define it by using the ‘acceptable’ diamond clarity grading system (VVS, VS or SI clarity) as it was already understood by most parties – gemologists, traders, and end consumers.

So, when GIA gemologists check emeralds in the lab. They classify the amount of filling inside the emeralds as described below:


If the presence of filled fissures substances fit into VVS2 to VS2 diamond clarity range then it will be classified as minor treatment.

This classification range is for the amount of filled substance inside the emerald and NOT the clarity of the stone.

In laymen’s terms, this means not too much substance is filled inside the emerald.   So, the foreign substance has not changed the clarity of the emerald by a significant amount.


If the presence of filled fissures corresponds to the SI1 to SI2 diamond clarity range then the emerald treatment will be classified as moderate treatment.


If the presence of filled fissures corresponds to below I1 diamond clarity range or above then this will be classified as a significant treatment.

Clarity enhancement as classified by GIA. These images were taken from the report issued Gems & Gemology Winter 1999 issues. (Photos were taken by Maha Tannous)
Clarity enhancement is classified by GIA. These images were taken from the report issued Gems & Gemology Winter 1999 issue. (Photos were taken by Maha Tannous)

Again the above criteria do not mean the emeralds are less included or more included.  It only states how much foreign substance has “entered” inside the emerald crystal.   To understand this more clearly, please look at the image above provided by GIA.

Another lab in the trade that classifies emeralds similar to the above criteria is GRS. GRS classification can be seen here:  https://www.gemresearch.ch/reports/enhancement-disclosure


When buying an emerald it is very important to check how much of the stone has been treated as this will affect the price.


If you are buying an emerald that isn’t too expensive, getting it verified from GIA or GRS can be overkill.  Both in terms of price and time.

However, if you are looking to get an emerald that has “no oil or resin” or has “minor oil or resin,” you should consider these labs.   As these types of emeralds command a higher price in general.

We also recommend that for any pricier emerald purchase, it is good practice to get a reliable third-party certificate.

We do not recommend using the smaller labs as they don’t have the equipment to tell the difference between “colorless oil” from higher-level treatments like color oil, dye, or resin.


We also recommend when buying less expensive emeralds ask pointed questions.  Either to the salesperson or dealer regarding treatments, and observe how they respond.

If they genuinely know what they are talking about and bring up similar points as discussed in this post, then you know you are dealing with someone genuine or knowledgeable.   Therefore, you have a higher chance of acquiring an emerald with ‘accurate’ levels of treatment as well.

However, if the person you are buying from states that their emeralds are “not treated,” then you should be extra careful.

Either the person selling to you does not know what they are talking about or they cannot be trusted.  We advise you to tread carefully with these people or to avoid dealing with them completely.
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14 thoughts on “Emerald Treatment Guide – No Oil, Minor, Moderate and Significant Treatment Emeralds”

  1. Sharon Hayes

    Hi, very good article and an interesting point about the cracks not reaching the surface and so you can be sure they have not been treated with oil. Thanks for sharing it.

  2. leuter

    Hello, imho picture 4 shows a natural 3 phase inclusion in columbian emerald .

  3. ravin

    I have emerald gemstone from Amazon.My friend recommend to check originality.so someone told me that I should heat them.so when I heat stone,it’s colorless .Is it fake or origenal??please tell me.

    1. Tom

      Fake. The dyed resin or oil came out

  4. Sherenne Powell

    Great article. Has just stopped me buying an heavily oiled stone glued into its setting. Thanks.

      1. Sohail Mohammad

        Hi I’m read ur feature on emerald it is very satisfactory.
        I also have some emerald from.pakistan utreated .
        I wanna sell it in food price if u can help me I will be grateful .
        Sohail Rana.

    1. Hi Maria,
      Good question and I don’t actually have definite answer to this question. In the trade or from any reputable lab, I haven’t seen anyone checking for heat treatment in emeralds and I am assuming the reason for this is because it does not respond well to this type of treatment. As Emeralds are typically ‘very included’ stones, I am assuming with heat treatment it will the cause the stone to shatter, which removes the purpose doing the treatment in the first place — too make the gemstone cleaner or have a better color. Also because they are very included stones they respond well with foreign liquid substances like oil, wax or other fillers. Again this will only work in emeralds with surface reaching fractures which allow the substance to flow inside the stone.
      Other beryls (same family as emeralds) like aquamarine and pink morganite are treated with heat treatment and it does enhance the color. But, these gemstones are typically very clean so I’m assuming there smaller risk in allowing the stone to shatter.
      Best Regards,
      Tarun Gupta, Graduate Gemologist (GIA)
      Managing Director of Thai Native Gems (1960) Co., Ltd.

  5. Pinky

    Are very small emeralds (like the size that would be on a wedding band) less likely to be treated than larger stones?

    1. thainativegems

      Hi Pinky,
      Unfortunately no. From the beginning emeralds in all sizes – smallest to biggest – are treated with some oil treatment. So, almost any emerald you see in a wedding band, etc., would have some treatment in it.
      Best Regards,
      Tarun Gupta, GIA GG

  6. Marie Abou Ewalyova

    Why they not leave it Natural, why they damige pure perfection? It is wrong

    1. thainativegems

      Hi Marie,

      Treatment is done because in general ‘natural’ emeralds are not very attractive and highly included, so oil treatment hides these inclusions.
      It makes gemstone easily saleable. But yes, I completely understand your perspective as well.

      Thanks for your comments and Best Regards,

      Tarun Gupta, GIA GG

  7. Marina

    You are right! I agree with you

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