Question about inclusions. 1 CT vs. 4 CT...

[Dancing Fire]

Let''s assume these are two idenitical stones with the same size inclusions, same location, the question is, would they both recieve the same clarity grade? In other words, does the bigger stone gets the advantage of having a bigger size inclusions, but still recieves the same grade as the smaller size.

 

[worldhistory]

From what I have learned the larger diamond would get a better grade because the inclusions are smaller in proportion to the size of the diamond. Lets say the inclusion is a 1 mm feather. It would look smaller in the larger diamond.

At least that is what I have learned in my search for and e-ring

 

[Richard Sherwood]

It's relative to the stone.

Let's say you've got an eyeclean 1 carat with a feather of a certain size, graded as an SI2.

If you were able to magically make that stone (and feather) grow to a 7 carat size, it would still be graded an SI2. The feather would still be the same size relative to the stone, although the inclusion might now be visible to the eye.

 

[valeria101]

Hm... this sounds like half the truth. Assuming GIA's procedures (and you can find comments on them among the "resources" at gia.org), the look of the respective inclusion would also count, and the size and coloration that make an inclusion visible does not depend on the size of the diamond around it.

There must be some balance between the two considerations (absolute and relative size of the inclusions), and one hears sometime words like "a VS-type inclusion" or "this SI grade is given by lots of VS-size inclusions" and so forth.

Granted, in a big stone there is more room for large inclusions that could not possibly be tucked into a 10 pointer - but this would be the case for lower clarity grades (I1 and over, I supose), and the aparence and area of stone affected by the stuff would be taken into account rather than each individual inclusion, since there would be so many anyway.

 

[Dancing Fire]

----------------
On 4/25/2004 10:38:29 AM Richard Sherwood wrote:

It's relative to the stone.

Let's say you've got an eyeclean 1 carat with a feather of a certain size, graded as an SI2.

If you were able to magically make that stone (and feather) grow to a 7 carat size, it would still be graded an SI2. The feather would still be the same size relative to the stone, although the inclusion might now be visible to the eye.----------------

Rich,
When you say eyeclean is that viewing from face up or from side view? It seems like it's pretty hard to find a stone that is not eyeclean. Can a stone still be graded as SI1 even with a dark inclusion near the middle of the table and a few near the girdle (SI1 according to the GIA cert)? Or does the inclusion have to be white to receive a SI1 grade? I can not see it with a naked eye but once I look at it with the loop, then I can spot it. The stone is beautifully cut. Maybe that's why I can not see the inclusions without a loop. It scored 1.1 on HCA.

 

[Richard Sherwood]

-----------
When you say eyeclean is that viewing from face up
or from side view?
-----------

Clarity grades are assigned on a face up basis. When viewed from the sides or table down the pavilion facets act like windows, letting you see into the stone much easier than face up.

-----------
Can a stone still be graded as SI1 even with a dark
inclusion near the middle of the table and a few
near the girdle (SI1 according to the GIA cert)?
-----------

Yes, definitely.

-----------
Or does the inclusion have to be white to receive a
SI1 grade?
-----------

No, plenty of SI1's have dark inclusions.

-----------
I can not see it with a naked eye but once I look at
it with the loop, then I can spot it.
-----------

Classic definition of an "eyeclean" stone.

-----------
The stone is beautifully cut. Maybe that's why I can
not see the inclusions without a loop.
-----------

The brilliance of a well cut diamond definitely plays a part in hiding inclusions.

-----------
It scored 1.1 on HCA.
-----------

Sweet... Congratulations. Sounds like a screamer.

 

[Rhino]

Reminds me when I was taking the advanced diamond grading class at GIA. The instructor had a slide of a 10ct stone up on the screen and there was an inclusion smack under the table of an emerald cut. He stated the inclusion WAS VISIBLE to the eye upon close examination. He asked the class what clarity grade they would assign to the diamond and almost everyone said I1. The stone was a VS2.




Rule of thumb: the larger the gemstone the easier it will be to look into it's facets.

 

[Dancing Fire]

----------------
On 4/25/2004 5:52:41 PM Richard Sherwood wrote:

-----------
When you say eyeclean is that viewing from face up
or from side view?
-----------

Clarity grades are assigned on a face up basis. When viewed from the sides or table down the pavilion facets act like windows, letting you see into the stone much easier than face up.

-----------
Can a stone still be graded as SI1 even with a dark
inclusion near the middle of the table and a few
near the girdle (SI1 according to the GIA cert)?
-----------

Yes, definitely.

-----------
Or does the inclusion have to be white to receive a
SI1 grade?
-----------

No, plenty of SI1's have dark inclusions.

-----------
I can not see it with a naked eye but once I look at
it with the loop, then I can spot it.
-----------

Classic definition of an 'eyeclean' stone.

-----------
The stone is beautifully cut. Maybe that's why I can
not see the inclusions without a loop.
-----------

The brilliance of a well cut diamond definitely plays a part in hiding inclusions.

-----------
It scored 1.1 on HCA.
-----------

Sweet... Congratulations. Sounds like a screamer.

----------------

Hi Rich,
Thanks for all the quick answers. How often do you actually get to see stones that are not eyeclean in SI grades? Boy, I must have Mr. Magoo's eye sight.

 

[Richard Sherwood]

-----------
How often do you actually get to see stones that are not eyeclean in SI
grades?
-----------

Not that often. Once in a while, especially in the larger sizes.

You've got to keep in mind the proper definition of "eyeclean". A stone that is considered eyeclean is one that the average person with average eyesight viewing the diamond under average lighting conditions at a distance of about 12 inches without having louped the stone first, and the inclusions can't be seen.

A lot of people will loupe a stone first under a powerful light source, locate the inclusion(s), then back off a couple inches, memorizing where they saw the inclusion under the loupe, and locate it with their naked eye (while still under the powerful light source).

This is not the proper technique for determining if a stone is "eyeclean". Nor is examining it from the side or table down, as inclusions easily show up in this manner.

 

[strmrdr]

one thing I wanted to add to the experts opinions and rhino hit on it.

There is a difference between the graded clarity and the effective clarity.
This is why I would never buy a diamond that I didnt see or have an expert I trust see before I bought it.

A friends wife has a diamond he bought for her that is a .45-.50 vs2
that has visible inclusions in some lighting and at certain angles.
The diamond acts as a magnifying glass and shows a very small inclusion as multiple large ones.
(I forget the exact size it has been a while)
Gia and 2 appraisers all grade it as vs2 so it isnt miss graded.
He isnt too happy that he paid a premium for the added clarity and the effective clarity is less than he paid for.
She wasnt very happy about it but grew to accept it and loves the diamond.

 

[Dancing Fire]

----------------
On 4/26/2004 8:15:08 AM Richard Sherwood wrote:

-----------
How often do you actually get to see stones that are not eyeclean in SI
grades?
-----------

Not that often. Once in a while, especially in the larger sizes.

You've got to keep in mind the proper definition of 'eyeclean'. A stone that is considered eyeclean is one that the average person with average eyesight viewing the diamond under average lighting conditions at a distance of about 12 inches without having louped the stone first, and the inclusions can't be seen.

A lot of people will loupe a stone first under a powerful light source, locate the inclusion(s), then back off a couple inches, memorizing where they saw the inclusion under the loupe, and locate it with their naked eye (while still under the powerful light source).

This is not the proper technique for determining if a stone is 'eyeclean'. Nor is examining it from the side or table down, as inclusions easily show up in this manner. ----------------

Rich,

So what you're saying is almost impossible to find a stone that is not eyeclean. It has to be a pretty bad stone for you to spot the inclusions from 12 inches away.

 

[Richard Sherwood]

-----------
So what you're saying is almost impossible to find a stone that is not
eyeclean. It has to be a pretty bad stone for you to spot the
inclusions from 12 inches away.
-----------

No, there's plenty of I1's, I2's & I3's out there which are not eyeclean. But you asked about SI stones. Most SI stones are eyeclean. Almost all SI1's are eyeclean, and the majority of SI2's.

 

[Magnum]

Rich or Rhino,
Hopefully you can answer this for me. This is straight from GIA's tutorial on their web site. On their "GIA Clarity Scale", it says:

"VERY SLIGHTLY INCLUDED
Contains minute inclusions such as small crystals, clouds, or feathers when observed with effort under 10X magnification.

SLIGHTLY INCLUDED
Contains inclusions (clouds, included crystals, knots, cavities, and feathers) that are noticeable to an experienced grader under 10X magnification."

Is there a more complete/accurate definition of the clarity grades out there, because going by these definitions, I don't see where the size of the stone or the relative size of the inclusions to the stones matters to the grading of the inclusions? A 0.1 mm inclusion will be the same size under 10X magnification whether or not the stone is 6mm or 10mm. If the GIA grades stones as you say they do, and I have no doubt that the info you both give is 100% accurate, then I would say that the information they are providing to the consumer is very misleading. If I were buying a 4 carat VS2 stone (I wish), than going by the info the GIA provides, I would expect that when I looked at the inclusions with a 10X loop, I would be able to see the inclusions "with effort under 10X magnification." I definitely appreciate any insite you can provide.
Thanks.

 

[Richard Sherwood]

Those are just quick one line descriptions meant to capture the essence of diamond grades in a "nutshell".

There's quite a bit more to it once you delve into the subject. The best course material on it would be the diamond grading courses offered by GIA or GAGB (Gemmological Association of Great Britain).

Regarding inclusions and their effect on clarity grade, all the following factors come into play:

Size, nature, number, color, location and effect on the structural integrity of the diamond.

Then you've got the extenuating circumstances of the size and shape of the diamond. Larger stones and step cut stones show inclusions more readily than smaller stones, while inclusions in very small stones are more difficult to see with the eye, loupe or microscope.

A case in point. The other day I was appraising a package of rings for a local jeweler. The rings contained diamonds ranging from a half-a-point to a point each. They were all I1 stones, yet, because they were so small, you couldn't see the inclusions with the naked eye.

The jeweler got quite upset with my grading, insisting that because the inclusions weren't visible with the naked eye, they were SI quality and better. (Actually, he insisted they were VS quality.) I showed him the size and nature of the inclusions under the scope, yet he said it didn't matter what I showed him under the scope, it was what he could or couldn't see with his naked eye that mattered.

A classic case of a little knowledge being dangerous. The jeweler had never taken the time or trouble to learn how to properly grade diamonds, and was selling jewelry based on incorrect assumptions.

Interestingly enough, he had paid "I1 prices" for all the rings. VS quality goods would have cost him considerable more.

The grading parameters commonly stated are for the size stones commonly encountered. Let's say from the 0.05 to 2.00 carat neighborhood. When you get into diamonds that are larger and smaller than this range, the size of the inclusion relative to the size of the diamond needs to be taken into account.

This is taught by the GIA in it's courses, yet not commonly stated in their literature for consumers. My guess is because it begins to make things complicated that they're trying to keep simple for the consumer. For all the nuances of diamond grading to be put forth to the general public, it would require an entire diamond grading course be published on their website instead of a concise description which covers most examples.

There's a couple great books on diamond grading available to the consumer who doesn't want to bother with the courses. I forget the exact names, but you can find them in the GIA Bookstore portion of their website. I think one is called the "ABC's Of Diamond Grading", and the other is written by a former lab grader/director. I believe his name is Gary Hoskins or Roskins or something along those lines. Great books which cover a lot of unusual diamond grading situations.

(I had finally had to look that jeweler in the eye and say, "Let me ask you something. Are you a gemologist?" "No? Well, let me know when you are. In the meantime, these stones are being appraised as I1's.")

 

[Magnum]

Rich,
Thank you very much for the quick and detailed response. It is very much appreciated. I learn something new almost everyday from you and the other expert posters here on pricescope. I've definitely thought about taking some of the GIA courses in the future, but those books might be a good start until I can work it into my schedule. Thanks for pointing them out. Have a good weekend

 

[valeria101]

There are quite a few articles on clariy grading listed on GIA's site. Not sure how practical they are, but surely enough to get the right feal of what an arcane process that is and exactly how much fine print needs removed to get down to the purpose and principle behind those clarity grades. No wander the two-lines definition makes so little sense!

Here are a couple such articles (the links go to review editions and the titles on clarity grading are obvious):

GIA Insider, June 06, 2003


GIA Insider, April 20, 2001


and there are more where these come from...