WHAT SOME DIAMOND SELLERS DON'T WANT YOU TO KNOW.

[Dancing Fire]

If the width and depth match perfectly you have created a perfect box to begin the math meaning if a diamond is (as an example)
60.04 depth 60.04 width then mathematically have you not created a perfect box to begin the calculation ?
From there all other angles relate in a mathematical way.

I'm still confused. I flunked all math classes in school..

 

[MollyMalone]

If the width and depth match perfectly you have created a perfect box to begin the math meaning if a diamond is (as an example)
60.04 depth 60.04 width then mathematically have you not created a perfect box to begin the calculation ?
From there all other angles relate in a mathematical way.

Let's work off a real GIA report so that we all can see what you mean in very concrete specifics. Here's one:
http://www.gia.edu/cs/Satellite?rep...ename=GIA/Dispatcher&c=Page&cid=1355954554547

(I've been thinking you were speaking of width & depth in mm, but your latest post suggests you're working in percentages)

 

[Jamiegems]

I am not a mathematician either but this is a simple proposition... you start with a box with perfectly square sides and top. That gives you the beginning of the math problem is all I am saying. The reason we have learned to control the light is the man that created the ideal cut did it by math and directing the light where he wanted it to go. In order to do that you have to have control and the box you begin with gives you that first calculation of control.

 

[Jamiegems]

OK that cert says that there is 3% difference in the depth to width so it's going to have pretty good refraction of light provided all the other angles are correct as well let me look at it again to see where the other measurements are.


OK on that stone it should be very good. The polish is excellent most of the other dimensions of the diamond are where they should be.
So I would say this diamond, is very nice and probably had very good fire to it. albeit that it is 3% off in depth to width
that is very close considering we have all seen diamonds that are far from those calculations.

so tell me this have you seen that diamond ? I am willing to say that that diamond has very good fire. Not perfect fire but very good.
Make sense ?

Your never going to see perfect, but if all the rules are followed and the math comes together then that cutter has controlled the light from the time it went in until it went back out the top again.

Also with the machines that we have now your going to see more and more diamonds that are closer to perfect than ever before. One of my best friends works at GIA and he cuts stones for a hobby. He uses math to cut them he follows a diagram from a book he has that is all mathematical problems. When he follows the math his stones come out with beautiful fire.

 

[Dancing Fire]

OK that cert says that there is 3% difference in the depth to width so it's going to have pretty good refraction of light provided all the other angles are correct as well let me look at it again to see where the other measurements are.

Where does it say that?

 

[Jamiegems]

6.58 - 6.61 < 59, 60, 61

let me look at it again to make sure

OR you can add the depth of the crown to the depth of the pavilion to get the entire depth
and then use the width of the crown you can do it either way but they have to be very close.

It doesn't matter how you get the measurements what you need to know is how deep is the entire stone and how wide is the entire stone.
and they should be close or the same which I admit is very hard to find one that is exactly the same width to depth.

Once you have those measurements you know how close to a perfect box your working with. After those two measurements are
found the rest is how do the other measurements and facets fit into the math problem

And even though this diamond is probably very nice The people I worked for would not by this stone because it's 3 not 2 or less.
It's just the way there were about their diamonds.

 

[MollyMalone]

6.58 - 6.61 < 59, 60, 61

let me look at it again to make sure

OR you can add the depth of the crown to the depth of the pavilion to get the entire depth
and then use the width of the crown you can do it either way but they have to be very close.

Tough to add the crown & pavilion depth measurements when the report doesn't supply those.

I'd expect that a GIA GG knows how to read a GIA report. 6.58-6.61 refers to its diameter in mm; the depth of that stone is 4.10 mm -- far outside your 2% rule.

 

[Jamiegems]

First of all in the lab you do have the instruments to measure that
and the certs have changed, but when I went there they gave the depth and width of the stone and I still stand by what i said.

if the depth and width of a stone are close or the same you are starting with a perfect mathematical box.
and they used to also have a photos of the stones as well. Nonetheless the math remains true to itself.
the ideal cut was designed by math not helter skelter .

It hasn't been that long I was there in 08.
but if what you say is correct then your right it is far from being within 2% or less. In the lab we measured the depth and width of every stone as well as all the other tests. With over 1600 diamonds.

And that is not a cert it's a diamond report which is a different document from a cert. It is a minor report on a diamond.
They do both.
There are actually 3 different reports and documents you can get from GIA.

 

[Jamiegems]

Dancing fire, Just know this

If you find the correct with and depth of a stone they should be very close or the same... that really is all you need to know.
Molly tried to trip me up with that report..

A diamond report is not the same as a cert. It makes some people happy to trip up someone that is as confident as I am about what I do.

Nonetheless just find those two measurements and make sure they are very close
and your on the road to a good start. It really is all math. not guess work. And it's not clever tweaking it's good old math that makes a diamond beautiful.

I ruffled too many feathers when I told the truth about the labs. But I was just trying to explain to people that GIA created
diamond grading. I think it's always better if people know the unvarnished truth. And now some of these people are out to get me for telling the truth.

I don't like to intimidate people but on this site I think many of these people mislead some of the innocent people that ask for help.
as teachers Gemologist should give people the truth. It flies in the face of many trade people for customers to know too much.
If people are empowered then they are more difficult to control. And everyone likes to think they are in control.
It may have been a mistake, but I am not sorry for writing this thread.

The truth is no matter who certs a stone the numbers still have to all work or you just don't get the proper end result.
When one of my friends goes to buy a diamond I go with them and look at the certs and I tell them if this stone will be good or bad and why it is either way. And a person should always see the diamond not just read unless you now how to read a cert. I pick all my diamonds from real certs and it has always worked for me. If the math is there the sparkle is there.

 

[MollyMalone]

GIA doesn't issue grading certificates/"certs"; they deliberately refuse to use that term. And if you wanted to see Diamond Grading Report #2125992110 (which BTW is for a Harry Winston stone) in all its glory, all you had to do was click the Download PDF button on the Report Check page I linked.

In any event, the way GIA reports a stone's Measurements has been a constant for years, regardless of the document, so it doesn't matter that you were at GIA in 2008. Your graduation date doesn't explain the goof you made.

Still, I remain interested in your precept & hope you will give us some links to diamonds you've found with reports & pics as examples of stones that do indeed fall within your 2% rule.

 

[Jamiegems]

I am not really interested in confrontation on this thread.
I told you what I learned and GIA changes report names and types whenever they choose. And I learned that concept from a store that would not buy any stone that wasn't within those parameters.

I misread the measurements but the math is the same. You needn't enjoy my GOOF as you call so much unless your just trying to embarrass someone for whatever reason. I don't do public displays of emotion or confrontation. The thread was for people who are confused about diamond grading how and where it's done.
I'm sorry you have decided to take me on in a confrontational manner. And i'm sure that you enjoyed exposing my GOOF as you call it. And I wasn't trying ruffle feathers when I was so honest about the labs. When the math is correct the end result will be what it should be. And we will see in the future much more precision in diamond cutting because of computers that will be doing it.

I've made more than one goof in my life and I am sure I will make more that doesn't invalidate my education at GIA.
I love what I do and I have done it all my life. And how is it that you know so much about GIA ?

 

[24caratsequin]

Because we know a lot more about diamonds than you appear willing to give us credit for?

I don't enjoy being condescended to.

 

[Jamiegems]

Well I am happy for you, and I don't condescend to anyone. Sounds more like self doubt than actual knowledge. You shouldn't be bothered by education. Or anyone that has it.

And who is we...do you speak for others as well as yourself ?

 

[denverappraiser]

Good morning Jamie,

I've been staying out of this because others have challenged several of your misstatements but one was skipped that I'm fairly sensitive to.

I am a Graduate Gemologist from GIA.

Then they call the managers Gemologist when all they have done is take a test from the company that tells them they are a Gemologist. Which I thought was a riot myself. But they could not certify a diamond in a court of law. And a GIA certified Gemologist CAN. THAT IS A BIG DIFFERENCE.

Jamiegems G. G.

GIA does not own the term 'Gemologist'. They weren't even the first to use it, although they were possibly the first to spell it that way. There are no licensing requirements associated with it.

GIA does not certify gemologists, in fact they specifically object to use of that term (GIA certified gemologist).

AGS, founded at the same time and by the same people who founded GIA, does have a title called 'certified gemologist'. A GIA-GG or equivalent, and yes there are equivalents out there, is a prerequisite to it. It's actually trademarked.

It's up to the courts to decide who they consider to be an expert and who they will allow to testify on a particular topic. The first step of any expert testimony is to qualify the expert. A GG would probably be accepted as expertise in certain gem related topics by most, but it's far from the end of the question and it's definitely not the only credential that's likely to be accepted. The FGA credential from Gem-A, for example, would be entirely acceptable in nearly every case. Accepting a particular witness as an expert is not the same as agreeing that their opinions are correct.

 

[John P]

Good morning all. (or afternoon, evening, nighttime depending on where you are).

Jamiegems, I think I understand now... The 2% example sounds much like the old 60-60 rule. It was used in stores for many years.

John the 2% rule is something that I learned even before I went to GIA. I was being groomed to work at a very high end jewelry store. The buyers would never buy any diamond unless the depth (the entire depth) and the width of the crown were within 2%.

Sounds similar... The 60-60 rule keeps depth% and table-width% within 2% of each other, close to 60%.
What's key is that the rule involves the width of the table facet (expressed as a percentage of diameter) not the width of the crown. Is that perhaps what you meant?

I took a few minutes to compose some examples. Dialogue is nice but a picture is worth 1000 words Hoping to arrive at better mutual understanding.

1. Example with Depth and Crown Width the same: (Impractical)

Here's what a diamond would look like if the total depth and total width of the crown made a perfect box.
As you can see that's not realistic, and about 1.50cts for only 6.50mm spread.

Purple arrows = total width (6.50mm) and total depth (6.50mm). Green arrows = box.



2. Diamond with Depth and Table Width the same: (60-60 GIA EX)

Here's a top 60-60 make, with complimentary pavilion & crown angles and minor facet choices.
The depth and table are 60% 60%. The angles support the critical window for light return edge to edge.
This would earn the top proportions grade at GIA, as well as the top light performance score at AGS.

Purple arrows = depth % (60.1%) and table % (60.0%). Purple circle shows GIA proportions grade.



3. Depth and Table Width the same: (60-60 GIA G)

But here is where the 60-60 rule is outdated.
Here again the depth and table are 60% 60%, but the angle choices miss the critical window, thus light escapes the diamond.
While it accommodates the 2% rule, it would only earn "Good" at GIA since 2006, and would be penalized to AGS 6.

Purple arrows = depth % (60.1%) and table % (60.0%). Purple circle shows GIA proportions grade.



4. Depth and Table Width different by 5%: (NTolk GIA EX)

Here, again, is where the 60-60 rule is outdated.
This is a diamond with proportions near one of the sets Marcel Tolkowsky postulated.
The depth and table are 61% 56%, so they are 5% apart.
But the complimentary proportions support the critical window and increase your chances of seeing fire.
This would earn the top proportions grade at GIA, as well as the top light performance score at AGS.

Purple arrows = depth % (61%) and table % (56.0%). Purple circle shows GIA proportions grade.



Hope it's interesting information.

 

[Texas Leaguer]

And if anyone needed to be reminded of what an extraordinary educator John is, there you have it. And the patience of Job to go along with masterful skill.

Well done teach!

 

[Dancing Fire]

Dancing fire, Just know this

If you find the correct with and depth of a stone they should be very close or the same... that really is all you need to know.
Molly tried to trip me up with that report..

Jamie
I still can't find a stone based on your 2% rule... so if the stone is 7mm in diameter i should look for a stone that is close to 7mm in depth?...

 

[John P]

Dancing fire, Just know this

If you find the correct with and depth of a stone they should be very close or the same... that really is all you need to know.
Molly tried to trip me up with that report..

Jamie
I still can't find a stone based on your 2% rule... so if the stone is 7mm in diameter i should look for a stone that is close to 7mm in depth?...

DF - Read my post above. Jamie will need to confirm, but I believe the ratio has to do with table-width and depth. Expressed as percentages. The old 60-60 rule. Frequently this was taught with a +/- 2% tolerance.

 

[John P]

And if anyone needed to be reminded of what an extraordinary educator John is, there you have it. And the patience of Job to go along with masterful skill.

Well done teach!

Tip of the hat, sir. Thanks for the kind words.

 

[Dancing Fire]

Dancing fire, Just know this

If you find the correct with and depth of a stone they should be very close or the same... that really is all you need to know.
Molly tried to trip me up with that report..

Jamie
I still can't find a stone based on your 2% rule... so if the stone is 7mm in diameter i should look for a stone that is close to 7mm in depth?...

DF - Read my post above. Jamie will need to confirm, but I believe the ratio has to do with table-width and depth. Expressed as percentages. The old 60-60 rule. Frequently this was taught with a +/- 2% tolerance.

JP...I knew that all along, but Jamie kept on referring to the measurements in MM ..

 

[Tekate]

AH BUT - what I know about Texas Leauger is who he is, he was willing to allow prosumers that knowledge... if I buy a ring or other jewelry from his company I know probably a minimum of 50 good reviews of his company and also postings of people who bought from him and/or employees and how happy the buyer is and also their pix of their new jewelry.. now you, you I don't know you from Adam.

Texas Leaguer

And stroking egos by telling uneducated people they are knowledgable isn't honest. I don't see any G. G after you name either. Just more opinions from a trade person.

jamiegems G. G.

 

[diamondseeker2006]

And if anyone needed to be reminded of what an extraordinary educator John is, there you have it. And the patience of Job to go along with masterful skill.

Well done teach!

Tip of the hat, sir. Thanks for the kind words.

You both are exceptional and I daresay know a lot more about diamond cut than the typical GG, apparently.

 

[MollyMalone]

Dancing fire, Just know this
If you find the correct with and depth of a stone they should be very close or the same... that really is all you need to know.
Molly tried to trip me up with that report..

Jamie
I still can't find a stone based on your 2% rule... so if the stone is 7mm in diameter i should look for a stone that is close to 7mm in depth?...

DF - Read my post above. Jamie will need to confirm, but I believe the ratio has to do with table-width and depth. Expressed as percentages. The old 60-60 rule. Frequently this was taught with a +/- 2% tolerance.

JP...I knew that all along, but Jamie kept on referring to the measurements in MM ..

Even after -- upon seeing her hypothetical with 60.04 width & 60.04 depth (nearly 2.4 inches in diameter) -- I suggested that maybe she was really working in percentages & proffered an actual GIA report for her to use.

I wasn't trying to "trip her up"; I actually was trying to give her an escape hatch, so to speak... that when she saw the report with percentages (and because I too initially was thinking she was advocating for a variant of the old 60-60 rule), she would say, "Oops, that was a brain fart (happens to everyone, right?). I meant you should calculate the ratio of table-depth percentages, not compare the entire width of the girdle with the stone's depth. Apologies for the confusion I inadvertently created!"

 

[MollyMalone]

John, thanks ever so much for all the diagrams & useful explanations, the visual aids are especially helpful!

ETA appreciation to Neil for his contribution re experts, etc.

GIA GGs don't all stand on the same footing -- eBay is littered with unreliable "appraisals" prepared by GGs

 

[Rhino]

John ... that first graphic.

Great post amigo.

 

[Karl_K]

I was going to have some fun then I saw Sir John beat me too it....
Of course he used more words than I would have
Good job.

 

[cflutist]

I was going to have some fun then I saw Sir John beat me too it....
Of course he used more words than I would have
Good job.

Yes, Sir John is a class act.
Most of the trade members and the Prosumers regularly posting on PS can run circles around our newest GG poster.

 

[Karl_K]

I was going to have some fun then I saw Sir John beat me too it....
Of course he used more words than I would have
Good job.

Yes, Sir John is a class act.
Most of the trade members and the Prosumers regularly posting on PS can run circles around our newest GG poster.

yep
What I find funny is PS is the most open place in the diamond industry and has been for a long time so its really the last place to rant about hiding things.
Any question someone has about the trade usually gets several good answers.

 

[Dancing Fire]

I was going to have some fun then I saw Sir John beat me too it....
Of course he used more words than I would have
Good job.

Yes, Sir John is a class act.
Most of the trade members and the Prosumers regularly posting on PS can run circles around our newest GG poster.

Cf...be nice and behave yourself...

 

[lovechild]

This is my first Dear John letter

Dear John,

Please elaborate on symmetry of an old cut (European) - if symmetry is rated "Poor" should I run screaming? This is in a 2 carat +/- stone, which "looks" pretty fabulous, but the GIA cert rating of symmetry is frightening me!

Thanks for any/all input! (I figured this was as good a place to ask this as any!)