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Round Diamond - last number in "Measurements"

bearcub907

Rough_Rock
Joined
Feb 21, 2016
Messages
24
Would someone be able to explain the significance of the last number in the "Measurements" in a GIA report? I understand that the first 2 are length and width and for a 1.5C round diamond, it should be ~7.4mm. But I am unclear about the last number and what it should be...

Sorry for the basic question! First time ring buyer and trying to learn as much as I can. Been learning a lot from these forums! Thank you all!
 

bearcub907

Rough_Rock
Joined
Feb 21, 2016
Messages
24
So I should focus more on the depth percentage rather than the depth in the "Measurements"

<62.3% for ideal cut..
 

Wink

Ideal_Rock
Trade
Joined
May 3, 2001
Messages
7,472
bearcub907|1456522625|3996259 said:
So I should focus more on the depth percentage rather than the depth in the "Measurements"

<62.3% for ideal cut..
Does not quite work like that.

You could have a perfect depth and still have a lifeless stone. It is a combination of the proper pavilion angle with the proper crown angel matched with a proper girdle measurement. When all is in balance then you will most likely get a pretty stone. if you have a proper crown and pavilion and an extremely thick girdle, you will have a fat ugly, lifeless stone. You must look at all of the angles and measurements to start to derive the beauty of the whole package.

Most of us, myself included, are not up to the "in our heads" mathematics and thus we like the ease and utility of the reflector images such as Ideal-Scope and ASET to tell us a LOT about the diamond in a split second.

However, in the end, you will need to see the diamond with YOUR eyes to determine if the diamond is for YOU. We can tell you what we think you will see or not see, but only YOU can tell us what YOU actually see.

The numbers are a nice start, and will help you identify diamonds worthy of an actual look, but the numbers alone do not tell the whole story. Is the diamond precisely cut and with the balance of one facet with another paired up all the way around the diamond to create a Hearts and Arrows pattern? Not told with the numbers. Does the diamond have a green or brown tint to it that will dramatically lower the price? Not told on the report. Does the diamond have CRISP on and off scintillation as the very beating of your heart causes it to move enough to sparkle? Not told in the numbers.

You MUST see the diamond to know for sure!

Learn the numbers, by all means, they will be a big help to you in choosing likely candidates, but they will NOT tell you the whole story.

Wink
 

diamondseeker2006

Super_Ideal_Rock
Premium
Joined
Jan 11, 2006
Messages
55,617
Yes, look at the depth percentage. I assume you have found measurement parameters since you know the 62.3, but I will post them for you just in case!

These are measurements to help you stay in ideal cut territory with a GIA excellent cut stone.

crown angle: 34-35.0

table: 54-58

depth: 60-62.3

pavilion angle: 40.6-40.9 (sometimes 41.0)


Also, there is a screening tool for GIA ex cut stones:

https://www.pricescope.com/tools/hca

You want to see Excellent on light return, fire, and scintillation, and very good on spread. An overall score of 2.0 or lower means a diamond is worth exploring further (but a 1.0 isn’t necessarily better than 1.9).

Then from there, idealscope or ASET images are super helpful in seeing if a stone has leakage or has great light return!
 

bearcub907

Rough_Rock
Joined
Feb 21, 2016
Messages
24
Thank you all so much!
I have narrowed my diamond search down to 3-4 diamonds. They all have excellent proportions (depth < 62.3, table 57, crown 34.5, pavilion 40.8) excellent sym, polish, faint or none fluro, and medium to slightly thick girdle.

I asked bluenile and James allen, and both do not provide idealscope or ASET images.

Then, would you be comfortable selecting a diamond based on the "ideal" numbers? I know James Allen lets you see the diamind up to 40x, but for someone like me, who is clearly not a diamond expect, I wouldn't be able to tell the difference between "good" vs a "very good" vs "excellent" diamond.
 

flyingpig

Ideal_Rock
Premium
Joined
Nov 7, 2015
Messages
2,171
bearcub907|1456674564|3996970 said:
Thank you all so much!
Then, would you be comfortable selecting a diamond based on the "ideal" numbers? I know James Allen lets you see the diamind up to 40x, but for someone like me, who is clearly not a diamond expect, I wouldn't be able to tell the difference between "good" vs a "very good" vs "excellent" diamond.
This really depends on the budget, price, return policy.
For a sub 1.0 carat or 5k, I may consider buying a stone without IS image, if the numbers and photo are good, and nothing from the report jumps out (ie knot, cavity inclusions, fluo etc...). That is JA.
From BN, the numbers have to be even more perfect, especially without a photo. I am talking 54-57 table, 40.6/35 or 40.8/34.5 combos. It has to be VS1 and no to faint fluo. In addition, the price needs to justify the risk buying a stone without a photo. There are other things I consider.

Other option is buying a AGS graded stone with AGS platinum report with coMputer generated ASET.

Regarding good vs very good vs ex, yes you will notice signifiant difference. You can simply go to a mall and compare. Or check out "good old gold" youtube channel
 

gr8leo87

Shiny_Rock
Joined
Apr 24, 2015
Messages
381
Re: Round Diamond - last number in "Measurements"

diamondseeker2006 said:
Yes, look at the depth percentage. I assume you have found measurement parameters since you know the 62.3, but I will post them for you just in case!

These are measurements to help you stay in ideal cut territory with a GIA excellent cut stone.

crown angle: 34-35.0

table: 54-58

depth: 60-62.3

pavilion angle: 40.6-40.9 (sometimes 41.0)


Also, there is a screening tool for GIA ex cut stones:

https://www.pricescope.com/tools/hca

You want to see Excellent on light return, fire, and scintillation, and very good on spread. An overall score of 2.0 or lower means a diamond is worth exploring further (but a 1.0 isn’t necessarily better than 1.9).

Then from there, idealscope or ASET images are super helpful in seeing if a stone has leakage or has great light return!
If you have reflector images to know light performance then you can safely throw HCA outta window. However this may not always be the case with every vendor providing you with those reflector images.
 

diamondseeker2006

Super_Ideal_Rock
Premium
Joined
Jan 11, 2006
Messages
55,617
Oh, certainly, gr8leo87. My assumption was that he was shopping through online vendors with no images at all, so he has to start narrowing down with numbers first!

I do know someone here who very successfully bought a nice diamond through BN with no images, but she was very strict with her parameters and went only with GIA Ex cut with 34.5 crown angle and 40.8 pavilion angle, because even with rounding, you generally are not in danger of getting a bad diamond with those numbers. While I personally prefer buying with light return images, I do think this is okay for those who prefer buying from vendors who do not provide them. Some people buy an idealscope or ASET scope and examine the stone themselves if they want to confirm the cut.
 

gr8leo87

Shiny_Rock
Joined
Apr 24, 2015
Messages
381
Re: Round Diamond - last number in "Measurements"

diamondseeker2006 said:
Oh, certainly, gr8leo87. My assumption was that he was shopping through online vendors with no images at all, so he has to start narrowing down with numbers first!

I do know someone here who very successfully bought a nice diamond through BN with no images, but she was very strict with her parameters and went only with GIA Ex cut with 34.5 crown angle and 40.8 pavilion angle, because even with rounding, you generally are not in danger of getting a bad diamond with those numbers. While I personally prefer buying with light return images, I do think this is okay for those who prefer buying from vendors who do not provide them. Some people buy an idealscope or ASET scope and examine the stone themselves if they want to confirm the cut.
Agreed one hundred percent.
 

bearcub907

Rough_Rock
Joined
Feb 21, 2016
Messages
24
This is so good to know.
I have contacted BN and they told me that they don't provide Idealscope images. And JA says they only provide for their signature diamonds.
So the 4 diamonds I have narrowed it down to, all have excellent sym, polish, fluoro. H color, VS1 or VS2, depth <62.3%, table <58%%, and CA/PA either ([34.5/40.8]; [34.5/41]; [34.5/41.2]; [34.5/41 (but this one has faint fluoro)], and girdle medium to slightly thick,

Am I missing something that I am being told that they don't provide those images? Because I am unable to see the diamond, I am making sure the numbers are good and not getting anything less than a VS2. Any input on this strategy?
 

gr8leo87

Shiny_Rock
Joined
Apr 24, 2015
Messages
381
Just a small tip - if your depth number is on the higher side try to get a diamond that has a smaller table.

For example depth 62.3 table 56 is better than depth 62.3 table 58.

This should be covered in those Crown and Pavilion angles automatically though. But it helps to know.
 

diamondseeker2006

Super_Ideal_Rock
Premium
Joined
Jan 11, 2006
Messages
55,617
bearcub907|1456796741|3997638 said:
This is so good to know.
I have contacted BN and they told me that they don't provide Idealscope images. And JA says they only provide for their signature diamonds.
So the 4 diamonds I have narrowed it down to, all have excellent sym, polish, fluoro. H color, VS1 or VS2, depth <62.3%, table <58%%, and CA/PA either ([34.5/40.8]; [34.5/41]; [34.5/41.2]; [34.5/41 (but this one has faint fluoro)], and girdle medium to slightly thick,

Am I missing something that I am being told that they don't provide those images? Because I am unable to see the diamond, I am making sure the numbers are good and not getting anything less than a VS2. Any input on this strategy?
You have a good chance of getting a good diamond with the 34.5/40.8. The others will not be safe with the 41 pav angle with 34.5 crown angles. So you are down to one diamond. What are the table and depth on that one?
 

bearcub907

Rough_Rock
Joined
Feb 21, 2016
Messages
24
The Depth is 61.8% and Table 57%.
H - VS1.
excellent sym and polish, no fluoro.
Thoughts?

Also, interesting that you mentioned the 34.5/41 won't provide good light return. I thought I read somewhere that some folks like 34.5/41 more than 34/41. Thoughts?
 

Diamond_Hawk

Brilliant_Rock
Trade
Joined
Apr 8, 2014
Messages
1,221
BearCub,

The reason you are getting a fair amount of 'hmm-ing' and people a bit reticent to tell you "Yes" or "No" is that the numbers really do not tell the entire story.

Every time the GIA lists the Crown Angle, it is an average of 8 measurements taken around the diamond. A 35 could be a perfect 35 all the way around, or it could be 34.2 at one measurement but a 35.6 at another, etc. etc. all coming to an average of 35. The same is true for the Pavilion Angle.

There is simply no way to know, for sure, what the light will do without a reflector image.

You can buy on the numbers alone, but it is somewhat like going on a blind date with the friend of a friend who is " '5 feet, 4 inches, brunette, and really pretty and super nice'. " Sounds promising, but you just have no idea, for sure, who you are meeting for dinner. Get as much information as you can to be safe.
 

bearcub907

Rough_Rock
Joined
Feb 21, 2016
Messages
24
If Blue Nile does not provide these images, then what do all the people do who buy from this website? Maybe that's where I am confused...

I have asked Blue Nile for these images and they tell me that they do not provide this.

Another option is to buy the diamond and find a local jeweler who would do this for me for a fee...

Thanks again! Really appreciate all the help.
 
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