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Diamond Enhancements

Edward Bristol

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Hello Everybody,


For ruby and sapphire, treatments (heat, diffusion etc.), or the lack thereof, are getting more and more important.


It seems, in diamonds that is different.


- Are there any estimates on the procentage of diamonds that have undergone some enhancement?

- If they are treated, are they mostly correctly labeled as such?

- Does a standard diamond certificate automatically state treatments?


I have been reading bits and pieces about diamond treatment (for clarity, color etc.) but can't find much data. Is there any online source you can recommend?

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Welcome to Diamond Review Edward,


The menu of choices for diamond treatments isn’t nearly as long as it is for some of these other stones but the rules are fundamentally the same. It must be disclosed at the point of sale. Some will affect the price drastically as compared to their untreated natural counterparts and others are more moderate. Customers for diamonds, like customers for most gemstones, very much prefer untreated natural stones. Most diamonds in the market qualify.


No, there isn’t really much of a centralized source of information about them. Perhaps someone here could write it. Maybe you. :rolleyes:


The biggies currently are:

Laser drilling

Acid bleaching

Irradiation to change the color

HPHT treatment to change the color

Fracture filling


Note: I know Edward. He’s a well qualified expert in ruby, sapphire and many other gemstones. Hermann, if he’s interested he would be a great boon to the site as a ‘verified jeweler’.



Edited by denverappraiser
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Thanks for the nice welcome!


I'd be interested in understanding more of the diamond world. Of course I am happy to share my know-how on ruby & co if helpful.


It seems that diamonds are not treated to the same extend as e.g. rubies are (where 99% are treated somehow)


I have gathered that AGS and GIA will grade laser-drilling, but will not grade fracture filling. The GIA will testify clarity treatments, but they will do no grading there. I am not sure what that means, yet.


Would heat or irradiation be detected in a normal diamond certification?


What does a heat process do to a rough diamond? What does irradiation?

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Most of the diamonds in the marketplace at the moment are untreated natural diamonds. Treatments have not been nearly as well accepted in the diamond business as they are with colored stones and stones tend to be more expensive (there are exceptions of course) and there is a lot more public information available which leads people to shop for them with a bit more care.


Heat treatment doesn’t do much of anything to diamonds.


Irradiation is used to alter the color in fancy colored diamonds. It’s generally pretty distinctive and it’s usually pretty easy to detect. Any credible lab will check for this.


Laser drilling is a bit more problematic. It’s not all that common but it’s getting more so and the drill holes are getting harder and harder to recognize as such. Up until a decade or so ago, this was not considered a treatment at all and then the FTC changed their policy and suddenly it was. As with the above, any credible lab will pick it up and will list it on their report.


Acid bleaching is often paired with laser drilling but occasionally it’s possible without it. This is using acids to dissolve out certain mineral inclusions and stains in order to make them lower relief. Technically it’s a treatment but I’ve never seen it disclosed as such. That is to say, I’ve never seen a stone disclosed as acid bleached without also having a laser disclosure although I know that such stones exist.


HPHT. High Pressure and High Temperature annealing. This changes the color and it’s impossible to detect using ‘standard’ gemological tools. I’ve seen them pass undetected through gem labs as well but the big boys will pick it up and report it. HPHT can be used both to make whiter stones as well as fancy colors.


All of the above will appear n the ‘comments’ section of most lab reports.


Fracture filling. This is where they fill surface reaching fractures and inclusions with a glasslike material in order to make them less visible. This is usually pretty easy to spot with a microscope or a loupe and the big labs won’t issue their standard grading reports to describe them. Some of the small labs make a living out of grading these.


‘Testify’ has to do with court work. They will identify a stone as being fracture filled but will not assign a grade ranking it against other stones, either filled or not.



Edited by denverappraiser
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