Back to IGS | FAQ | Contact

ExCel Emerald Enhancement Process

I’m interested in determining a consensus amongst professionals regarding their attitudes toward the ExCel Emerald Enhancement Process as opposed to standard and accepted oiling practices.

As an industry pro, do you feel that the ExCel process increases or decreases the value of the stone?

1 Like

This process is said to enhance and make emeralds more stable.
Especially while being worked on at the bench.
Sounds like what Yehuda has done to lower quality diamonds.
As we all know 90% of colored stones have already been enhanced and
should remain stable. This practice has been used for many years. Even
with this process, colored stones still demand a high price. On the other hand
Yehuda diamonds only increase in value due to the process. I never sell jewelry
for investments and the value is in the ownership. I would rather sale the excel emerald
due to the stability, just like we sell rubies that have been enhanced. I always disclose
what the customer is buying in full detail.

The intended purpose of ALL clarity enhancements in emeralds is to infill and mask as much of the visible internal fissures as possible. Any such treatments create a “value added” effect (it is an expense to treat it after all).

But it’s the extent of the treatment (how much the inclusions were masked) that determine the emerald’s original condition, and ultimate value. Whether minor, moderate or extensive, these levels of treatments are able to be seen by an effective laboratory, and commented upon within a report.

So the real question might be, "what is the best method (product) for emerald clarification?

Wearing my laboratory director’s hat I would have to admit (for a number of reasons) that the ExCel product is the most effective, and stable method available for emerald clarity enhancement.

1 Like

Thanks to both of you. Your opinions are much appreciated

I looked at a GemWorld article by Stuart M. Robertson, GG, written in 2007. The GemWorld article described the process of treating rough emerald with polymer (ExCel is a polymer treatment) prior to cutting to enable emeralds that might otherwise crumble on the wheel to remain intact. This process caused a scandal and was viewed as fraud. Acceptable treatment was viewed as one which could be removed…and rough that was stabilized prior to cutting could not be guaranteed to stay together if the resin were removed. So the only acceptable treatments would be those done after cutting. Robertson goes on to state:
“Significant premiums are no longer associated directly with the type of filler used. However, market
participants may have individual preferences concerning the type of fillers they will accept.”
You would have to clarify with ExCel, but I believe they only treat cut stones. Robertson says that the extent of filling is an issue and only stones which have a moderate level of enhancement bring the prices quoted in the GemWorld Guide. Those with only a slight degree of enhancement would draw a premium and unenhanced stones would bring 50% to 100% more than the Guide price. While this is an old article, I don’t see where the Guide has updated it, so it may still be current thinking for them. I suppose some people would still prefer cedarwood oil or Canadian balsam and others would go with polymers which would probably be more stable in the long run, but I would think the ultimate issue would be to have a lab tell you about the level and type of treatment. I think ExCel is guaranteed to be permanent, so that is a selling point for it. I don’t have experience with buying or selling high end emeralds, so quoting this article is the best I can do.

Thanx royjohn,

It appears the Clarity Enhancement Laboratory is the only lab that offers the proprietary ExCel process.

According to their web site :" ExCel is a polymer with the refractive index similar to an emerald. It is capable of withstanding ultrasonic baths, steam cleaning and the re-polishing process without any changes to its appearance. It is also removable if needed without any adverse effect to its host stone." The site also advertises a lifetime guarantee.

If I recall correctly, GIA uses only three enhancement grades “slight, moderate and significant” and refers the reader to the QR code at the bottom of the report for more info. I would imagine this process would garner a ‘significant’ rating, and that’s what prompted my original post.
Thank you again.

Hi Dennis,
I don’t know that much about emerald treatments, but I don’t think that just because it is a polymer that it is a bigger treatment. That’s why Robertson says in his article that the material that is used is not an issue, just the extent of the treatment. If the emerald doesn’t have visible fissures and merely has very small cracks that would be filled and made less visible with oil, I would guess that you could do the same thing with polymer. Yes, polymer can be used to fill large cracks and even to stabilize rough that is falling apart and can’t be cut without basically being glued back together does not mean that polymer can’t be used to do “slight” treatment. The supposed advantage of polymer is that it is stable over time and doesn’t yellow or fall out or be driven out with ultrasonics or steam. I have known people to have their emeralds cleaned and find that the oil was cleaned out of them with a great loss in clarity. Canadian balsam in old camera lenses will begin to crystalize and the glued lenses will separate. Oils like cedarwood can, I think, discolor. One would think that the advantage of balsam or oil is that it is easily removed, but if the ExCel polymer is removable and more stable, perhaps it is actually better. You would need a good lab report to tell you the extent of the treatment.
If you are concerned about this, I think you could give GIA a call and ask whether they differentiate between treatments or not as to whether one of the other is preferred. I think they would tell you.