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Strain: Just how important is it anyway?

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rookie

Rough_Rock
Joined
Feb 12, 2003
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8
I''m getting closer and closer to finding the right rock and I''ve now come across a new term...."strain". I''m told it''s real important to get an independent test done prior to buying that includes an analysis of strain. When i mentioned this to the retailer, they said it''s not important unless the diamond is heavily included. Help!!!
 

StevL

Brilliant_Rock
Trade
Joined
Dec 31, 1999
Messages
598
Sounds as though you have been speaking to one particular appraiser and he believes what he says about strain.

But............

I have never heard anything by either of the big two labs that strain should be a concern if the diamond made it through mining and cutting. I tend to agree and it would not be a big concern to me.

I would assume any engagement ring purchase would be a rather large jewelry purchase for anyone. With that said I would purchase insurance through your homeowners or another insurance company of choice.
 

rookie

Rough_Rock
Joined
Feb 12, 2003
Messages
8
Steve, thanks for the reply. When you mention insurance my curiosity gets peaked. From your reply, I am inferring that strain could result in a damaged diamond?
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,332
Steve is correct, one appraiser whose name you already know, and will probably not be able to resist appearing to defend his position, makes this claim.

It is unsubstantiated by the literature or many cutters who have debated the topic endlessly.

do a search on this topic and you should make your own assessment.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,272
Haha... yes. There are great debates on the subject. In the over 2 decades we've been serving our clients I've never personally seen a stone break as a result of it. If it is a concern of our clients we will preinspect the stones they are considering and only show or suggest stones without strain as we can check for that in our lab prior to sending stones out for appraisal.

Rhino
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,272
Haha... amen to that Rich.

I know Bill thinks it is more serious but after the amount of people I've spoken to on the subject and the reading I've done I've concluded that it's not so serious.

Interesting fact though. In the GIA Diamond dictionary it does state (if memory serves me right) that lower prices on negotiated on rough with strain. I can understand this since the CUTTER is the one at risk since he will be putting the diamond through further heat and pressure on the cutting wheel. However, after the diamond crystal has been put through the amount of stress through it's crystalization proces in the earth and the stress of the cutters wheel, the opinion of most in this industry is that since the crystal has survived to this point, there is NO consumer who'll put their diamond through the same strenous conditions it's been under up to the point till it's got on their finger. I am currently of this opinion unless I can be convinced otherwise. In our 22 years we've never seen one break because of it.

If you would like to see pictures of the phenomena I've taken some nice shots of it which is included in our chapters on clarity, particularly the "gallery of inclusions". They are the last pics on the page which I've taken under a polarizing filter. Here's the link.

http://www.goodoldgold.com/gallery_of_inclusions.htm

Enjoy,
Rhino
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
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Messages
15,332
Rhino I have seen rough that shows strain to the naked eye. As you say this rough would have little chance of surviving the stress and heat of bruting and the cutters wheel – so of course it will be worth less.
They use this stuff in mining drill tips because they keep breaking away to new jagged edges. If it does get cut it is sold as knat’s – no one is ever going to certify this stuff.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
Rhino if your site gets any more complete, I think you should start teaching your own version of the GIA diamond essentials course...except it would be the GOG Diamond Essentials Course. hee hee. It's a great supplement right now anyway!
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Yeah half the time I don't know the answer to a question, I go to Rhino's site, get the answer, and take all the credit.

Heh heh heh... I'll buy you dinner some day, Rhino. Your choice- Burger King, or McDonald's.
 

rookie

Rough_Rock
Joined
Feb 12, 2003
Messages
8
Thanks everyone, really helpful. One more question. Is a crown angle of 34.1 to be concerned about. The pavilion angle is 40.7 The stone shows well on the HCA---.7! but I wondered at the crown angle, especially when I've read that the Tolkowsky ideal is 34.5. Thanks
 

StevL

Brilliant_Rock
Trade
Joined
Dec 31, 1999
Messages
598
rookie,
I would make that suggestion to anyone with any diamond (branded or not, ideal or not). They all can be broken, chipped, lost, or stolen.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
34.1 crown angle should be just fine ...the range for a desirable crown angle is not limited to one number, but it also depends on your pav angle as well and how the two relate together. For example my crown angle is 29.9...shallow. But my pav angle is right on the money for my stone, I think it is 41.1, if it was 42 then chances are the stone would not look as good as it does. Keep in mind also that the Tolowsky ideal gives ONE combination of possible angles for an ideal stone...but there are many more than one creating an excellent stone.
 

jlim

Shiny_Rock
Joined
Apr 29, 2003
Messages
250
----------------
For example my crown angle is 29.9...shallow. But my pav angle is right on the money for my stone, I think it is 41.1, if it was 42 then chances are the stone would not look as good as it does.
----------------
Any gemologist, esp. D. Atlas care to comment on this? I looked up the table on your website and it says 29.9 Crown Angle is essentially a 3B. Can an excellent pav. angle compensate for a shallow crown angle?
 

Caratz

Shiny_Rock
Joined
Jun 4, 2002
Messages
222
If I understand Rockdoc's position on strain correctly, it goes something like this: Strain may or may not affect the durability of a diamond, but if a diamond is chipped and the chip might be linked to the presence of strain, then the insurance company might deny a claim on the basis of a pre-existing condition. Therefore it is better to avoid stones that might tempt an insurance company to deny a claim.

I think that Rockdoc's advice is valid if you are buying a million dollar stone, as an insurance company would have a good incentive to avoid paying the claim. However, for a stone valued at "only" a few thousand dollars, an insurance company is simply not going to refuse a claim based on such a questionable "defect" (to date, as far as anyone knows, no insurance company has ever taken such a position). It's just not worth it. If anything, I think you are WORSE off by icluding a strain analysis in the appraisal, as this invites an insurance company to deny coverage where it otherwise wouldn't even bother to think about it. Just my two cents.
 

caratgirl

Brilliant_Rock
Joined
Jan 1, 2003
Messages
634
Caratz,

I agree about not including strain issues into an insurance appraisal report. What a red flag that would be! I hope that a strain report is issued separately...anyone that has one care to comment? I don't have a strain report, so don't know.
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
-----------
Any gemologist, esp. D. Atlas care to comment on this? I looked up the
table on your website and it says 29.9 Crown Angle is essentially a
3B. Can an excellent pav. angle compensate for a shallow crown angle?
-----------

The brilliance of a diamond corresponds directly to the relationship between the crown and pavilion angle. It's not so much a question of whether an "excellent" pavilion angle can compensate for a shallow crown angle, but what is the most complimentary pavilion angle for that particular shallow crown angle.

If a crown angle goes shallower, the pavilion angle needs to go deeper in order to keep the same brilliance. I think I remember reading the relationship is like 4 to 1, with the pavilion angle being the most important. If the pavilion angle goes .1 degree deeper, the corresponding ideal crown angle would drop .4 degree shallower.

This would keep the light return looking good, but not remove it out of the 3B category because of the technical aspect of make. As I remember Dave explaining it, the integrity of the make plays as much a part in the cut grading as brilliancey factors do. A shallower crown angle threatens a greater vulnerability to chipping, hence receives a lower grade.

A good example of the crown-pavilion relationship can be found in the PriceScope tutorial at:

https://www.pricescope.com/tutor_crn_pav.asp
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
That crown-pavilion angle relationship, by the way, explains the cause of the dreaded "ring of death" in steep-deep stones.

The pavilion is headed toward the deep side (greater angle), and should be compensated for with a correspondingly shallower crown angle. Instead, the crown angle wanders in the opposite direction, to a steeper angle. The pavilion angle is calling it to come closer, but the crown angle is responding to the beat of a different drummer, the cutter who's trying to conserve weight instead of attain ultimate brilliance.

This creates massive light leakage just inside the table, resulting in what Rhino has dubbed "the ring of death".

An epic battle of opposing forces, weight retention versus brilliance. Like the Middle East struggle, it's not likely to end soon.
 

Final Cut

Rough_Rock
Joined
Apr 21, 2003
Messages
85
The issue of strain is interesting though .... because .... just like the "Previously hidden - now with PS and HCA out of the closet" issue of CUT, it makes sense intuitively....

So if you ask any of the experts here on the forum ... how did you start focusing on CUT exactly ... they will all say .. it is obvious ... now !

I am surprised that noone can conclusively work out whether strain exists when a particular stone tests positive for strain and what that means ... after all it seems like the experts on this board are among the leading in the World.... is it because you don't consider it important ? or because you don't think it exists ?

Interesting - just my 2 feathers..

FC


 

AGBF

Super_Ideal_Rock
Premium
Joined
Jan 26, 2003
Messages
21,385
Rich,

I always liked that picture of you. What kind of hat is that? Is it a gemologist hat? What's on the visor? I recently saw a Woody Allen movie in which he plays a petty crook whose wife's cookies catapult him to great wealth. In one scene he and another crook are digging a tunnel (they *think* into a bank). Woody Allen notices Crook #2 is wearing his hat with the light turned towards his back (as he tunnels) because it "looks cooler".

Why did I feel I had to share that?
 

Rank Amateur

Brilliant_Rock
Joined
Feb 26, 2003
Messages
1,553
Those are Rich's gemologist goo goo goggles. G...g...g.

It was either those magnifying goggles or have Lasik on one eye to bring it up to 10x.
 

fire&ice

Ideal_Rock
Joined
Jul 22, 2002
Messages
7,828
----------------
On 5/21/2003 7:34:46 PM Richard Sherwood wrote:

AGBF, that jeweler's visor is what my wife refers to as my "other appendage" because it seems to be attached to my head permanently.

----------------
When we go on vacation, Hubby must have his cell phone surgically removed under my direct orders.
 

barry

Shiny_Rock
Joined
Mar 21, 2001
Messages
441
HaHa, fire &ice;

I know just what you mean.

Last summer, on vacation with the missus
and 3 other couples (friends) I really overdid
the cellphone shtick, (head down wandering
aimlessly away from the group, engrossed in
conversation) constantly on it
back to NY. There's a great shot of me on
the cell, right hand in the air with
the seven others lined up behind me,
cell phones and right hands in the same position.
The Wife entitled the Picture: "My Summer Vacation".

She's warned me that if I do it again this
summer, there will be surgery; but it won't be the ear.
(No, her name is not Lorena).

Hay Caramba!

Barry
www.superbcert.com
 
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