Strain vs. Graining

[gingercurls]

Hi everyone. My best friend is getting engaged! Her soon to be fiance asked me to help pick out a diamond for the ring after he had a confusing conversation with a jeweler. I told him that I would ask for clarification here for him.

One of the diamonds that he was looking at had internal graining noted on the GIA report. The jeweler apparently told him that internal grading is not the same as strain in a diamond and is therefore not an issue. Another person working in the store then said that actually graining and strain are the same thing. He left confused and when he explained this to me, I did some Googling but was not able find a clear answer. In short, are graining and strain the same thing? If a diamond does not have graining noted on the GIA report does that mean it does not have any strain? To clarify, I am referring to earth mined, natural diamonds and not lab made diamonds.

Thank you!

 

[DejaWiz]

From what I understand, they are different characteristics.
Strain is an internal tensile force self-exerted on the formation morphology of the crystalline lattice of the diamond and could result in ease of shattering.
Grain is unique growth patterning of the crystalline lattice and may or may not be under strain.

 

[gingercurls]

Thank you for the reply @DejaWiz Is there a person/appraisal company that anyone on the forum recommends that can check a diamond for strain?

 

[gingercurls]

Or is there something that a consumer to use to determine if a diamond has strain present?

 

[John Pollard]

The presence of internal strain can only be seen using a polariscope or cross polarized filters. Even if present, it's not noted on the grading report.

The reason strain doesn't appear on grading reports is because it's a topic for researchers - studying formation and transport history - and diamond cutters. It's not considered a consumer concern because a finished diamond has undergone stress and trauma in the sawing, girdling, blocking and polishing process that it will never see again in normal wear.

Graining is a clarity feature. It's associated with crystal lattice discontinuities in a diamond, so it can be considered a cousin to strain, but practically all diamonds have discontinuities. For the record, whitish graining is associated with dislocations in the lattice which happened during its growth process, due to temperature-created stressors, and remained there after the stress was released. Reflective graining is similar but occurred at the edge of a grain boundary, where sides slipped relative to each other, and is frequently only observable from a specific direction.

If the comment "clarity grade based on internal graining not shown" exists on the report, and the diamond is below the VS clarity category, further analysis may be warranted - as much for optical interference with refraction as for a durability concern. In the big picture, however, incidental graining is benign.

 

[gingercurls]

Hi @John Pollard Thank you so much for replying. Based on your reply, if my friend wanted to have his potential diamond evaluated, he should go to a person (gemology, appraiser...) and request that they view the stone using a polariscope or cross polarized filters correct?

 

[John Pollard]

Based on your reply, if my friend wanted to have his potential diamond evaluated, he should go to a person (gemology, appraiser...) and request that they view the stone using a polariscope or cross polarized filters correct?

If your friend has concerns an independent appraiser/gemologist with that equipment could alleviate them. This is not a typical appraisal component, however, so you'd need to ask, specifically, whether the appraiser is equipped to do this.

Before going to that expense, it would be interesting to know what motivated this comment.

Another person working in the store then said that actually graining and strain are the same thing.

What is the clarity grade? Is there a comment on the GIA report indicating the clarity grade was based on graining?

Some stereotypes exist regarding topics like this, fluorescence, feathers, etc., wherein any diamond with one of those components is painted negatively impacted. In reality it's always case by case - and for clarity related components the first thing to look at is the diamond's overall clarity grade and laboratory comments.

 

[gingercurls]

Hi John. That is a good question. I was not with my friend when he was at the jewelry store. Based on what he described, it seemed like it was just an offhand remark that the other person made. My friend was looking at two diamonds. Both were graded internally flawless but one of them had a comment about graining not being shown.

 

[John Pollard]

Hi John. That is a good question. I was not with my friend when he was at the jewelry store. Based on what he described, it seemed like it was just an offhand remark that the other person made. My friend was looking at two diamonds. Both were graded internally flawless but one of them had a comment about graining not being shown.

If the diamond is IF the comment refers to surface graining. No issue whatsoever.

 

[gingercurls]

Thank you John. I very much appreciate it! This will probably be (another) silly question but could a GIA graded internally flawless diamond without any report comments regarding surface or internal graining have strain?

 

[John Pollard]

Thank you John. I very much appreciate it! This will probably be (another) silly question but could a GIA graded internally flawless diamond without any report comments regarding surface or internal graining have strain?

Natural diamonds grew under extreme heat and pressure. It's possible for any diamond to have strain. When I operated a diamond re-cutting service I'd always have candidate stones checked. The presence of strain was extremely rare, even in low clarities, to the point where I can't recall a single domestic recut where that factor prevented improvement.

Keeping this in context. Bear in mind that strain - if present - only poses a durability risk when there is enough duress at some release point to cause a fracture. An IF diamond has no release points. External areas come under pressure during the setting process, but as long as you buy the diamond and mounting in the same place the jewelry store should have coverage against (remote) damage caused during setting.

Also, the reason diamond setters have that coverage has to do with cleavage planes and corners. All diamonds have cleavage planes. Even the most Flawless diamond can chip if you knock it against something the wrong way. Shapes like princess and marquise have sharp, fragile corners which need to be treated carefully during the setting process.

Bottom line? Any diamond can be damaged if struck the wrong way. This is why it's good to have your precious diamond jewelry insured, just as you would your house or car.

On that topic: There's a link on this page if you're interested in getting a quote from Jeweler's Mutual.

 

[Texas Leaguer]

Thank you John. I very much appreciate it! This will probably be (another) silly question but could a GIA graded internally flawless diamond without any report comments regarding surface or internal graining have strain?

John gave a very thorough explanation of the technical and practical issues with strain. It's really a non-issue for a shopper for a faceted diamond, for the reasons he explained.

In regards to your last question, theoretically an internally flawless diamond could have strain. The clarity call is a visual one, based on inclusions that can be physically seen under 10x magnification. Since strain is not an inclusion and can only be indirectly detected as an anomaly of light viewed through polarizing filters, it would not keep a diamond from being graded as FL or IF.

 

[gingercurls]

Thank you all so much for the replies and information. I will do my best to explain everything to my friend to make his search easier. If one of the diamonds he is considering is already mounted, would it still be possible for an appraiser or gemologist to use a polariscope to check if the diamond has graining?

 

[foxinsox]

Thank you all so much for the replies and information. I will do my best to explain everything to my friend to make his search easier. If one of the diamonds he is considering is already mounted, would it still be possible for an appraiser or gemologist to use a polariscope to check if the diamond has graining?

The polariscope is used for detecting strain which is a non-issue for a consumer once a diamond has been cut, polished, faceted and set etc.
Graining would be noted in the grading report and is not usually an issue if the clarity grade is VS or better if I’ve understood the discussion this far. So no need for a polariscope for an appraisal.
It might be easier to just point your friend at this thread so he can read the difference between grain and strain and why the latter isn’t an issue.

 

[gingercurls]

That is excellent advice @foxinsox !