grading questions

[Cehrabehra]

I have some random GIA grading questions but I''ll start with the first...

... is a stone graded by ONE person all the way through or do different people grade differnet parts like color and flour and clarity and sizes etc?

Is it possible to see VS2 inclusions unaided? I''m pretty sensitive to what look like "bubbles" to me - they''re clear but they''re like champagne bubbles... the tiny black dots can actually be harder for me to spot when they''re small. What are those bubbly things called? The clear inclusions?

If GIA uses sarin and the vendor uses sarin - why are the numbers sometimes off a bit? It seems like they should be able to be rock solid... my husband is in computers and deals in nanometers all the time where they have 100% accuracy... of course his machines cost 250k and I doubt most appraisers have that sort of funding, but still... just curious about that... I''m SURE it''s been hashed out in a thread but I''m not sure what I''d search for! lol

 

[aljdewey]

Date: 8/26/2006 1:05:00 AM
Author:Cehrabehra

... is a stone graded by ONE person all the way through or do different people grade differnet parts like color and flour and clarity and sizes etc?

They are graded by several people in the grading lab.

Is it possible to see VS2 inclusions unaided? I''m pretty sensitive to what look like ''bubbles'' to me - they''re clear but they''re like champagne bubbles... the tiny black dots can actually be harder for me to spot when they''re small. What are those bubbly things called? The clear inclusions?

It''s less likely to VS2 inclusions unaided, but for those with acute vision, it may still be possible, particularly from the side view. The ''champagne bubbles'' are likely pinpoints.

If GIA uses sarin and the vendor uses sarin - why are the numbers sometimes off a bit? It seems like they should be able to be rock solid... my husband is in computers and deals in nanometers all the time where they have 100% accuracy...

There is no such thing at 100% accurate.

Sarins are machines and, like other fine equipment, require regular calibration to be effective. Even within that framework, it''s impossible for every Sarin to read precisely the same.....just like it''s impossible to get every watch to run precisely the same.

 

[Cehrabehra]

Date: 8/26/2006 1:28:26 AM
Author: aljdewey

Date: 8/26/2006 1:05:00 AM
Author:Cehrabehra

... is a stone graded by ONE person all the way through or do different people grade differnet parts like color and flour and clarity and sizes etc?

They are graded by several people in the grading lab.

Is it possible to see VS2 inclusions unaided? I''m pretty sensitive to what look like ''bubbles'' to me - they''re clear but they''re like champagne bubbles... the tiny black dots can actually be harder for me to spot when they''re small. What are those bubbly things called? The clear inclusions?

It''s less likely to VS2 inclusions unaided, but for those with acute vision, it may still be possible, particularly from the side view. The ''champagne bubbles'' are likely pinpoints.

If GIA uses sarin and the vendor uses sarin - why are the numbers sometimes off a bit? It seems like they should be able to be rock solid... my husband is in computers and deals in nanometers all the time where they have 100% accuracy...

There is no such thing at 100% accurate.

Sarins are machines and, like other fine equipment, require regular calibration to be effective. Even within that framework, it''s impossible for every Sarin to read precisely the same.....just like it''s impossible to get every watch to run precisely the same.

ahhh from one machine to the next yes, esp. if they''re owned/maintained by different people... my dh''s job is basically making sure that everything IS exactly the same, not only on his tools but on the same tools around the world... he was twirked about the inaccuracy but I told him people who know way more about diamonds than he have argued about it I''m sure and are doing the best they can lol

I always thought pinpoints were black but I really don''t know much about the types of inclusions and what they''re called... I''ve SEEN many types but I kept my mouth shut in the stores and didn''t ask what they were called. I wonder if there is a PS thread that showcases types of inclusion LOL
~visual>

 

[Giangi]

I just want to point out that visibility of inclusions is greatly related to the size of the stone. On a 3ct stone, it wouldn''t be that unusual to be able to spot a very small inclusion, especially if you knew where to look. There are always exceptions to the rule and there is really no definitive method when it comes to clarity grading.
As for the Sarin questions, Alj''s answer -as usual- said it all.

 

[oldminer]

Visibility of inclusions relates to their size, relief and location within a given stone. It also is hugely elated to the lighting conditions present. We find inclusions much easier in the microscope using both our eyes than we do using a loupe, too.

There are many techniques and approaches to try. One uses those which work best for the particular stone they are examining.

Every once in a great while we use immersion to diminish surface reflections. THis is a dificult technioque but a valuable part of the bag of tricks.

 

[Cehrabehra]

Date: 8/26/2006 4:52:04 PM
Author: oldminer
Visibility of inclusions relates to their size, relief and location within a given stone. It also is hugely elated to the lighting conditions present. We find inclusions much easier in the microscope using both our eyes than we do using a loupe, too.

There are many techniques and approaches to try. One uses those which work best for the particular stone they are examining.

Every once in a great while we use immersion to diminish surface reflections. THis is a dificult technioque but a valuable part of the bag of tricks.

I ask because I am sensitive to inclusions in general... RBs hide them pretty well, but since I''m looking at an OMC I imagine they don''t hide well at all... so here''s another question: Is the grading done based on each stone or something general... I mean what would be eyeclean in a RB wouldn''t necessarily be so in an emerald cut. And like you guys mentioned, what might be eyeclean in a 3/4 carat might not be eyeclean in a 3 carat. So is the VS, SI scales based on percentages of inclusions or if you can see them with the eye or... what I''m getting from the comments here is that it is set and makes no difference on cut or size... so if you have a 3 carat EC VS2 really might NOT be eyeclean, possibly even often might not be, even if in a 1c RB it almost always is.

 

[Anthony K]

Now it really is not fair for you to try and compair a RB and an EC because you will only confuse your self and feel more stressed out. A Emerald is a step cut and you kinda need to think of it like layers of glass stacked on one another, they dont reflect alot of light back (deffinatly not the way a Round does) and you can see right through them, and thats why that even with a VS you may still see inclusions where as a RB reflect the light back and causes the inclusions to get lost.

Hope this helps.

Anthony K

 

[Cehrabehra]

Date: 8/26/2006 9:27:48 PM
Author: Anthony K
Now it really is not fair for you to try and compair a RB and an EC because you will only confuse your self and feel more stressed out. A Emerald is a step cut and you kinda need to think of it like layers of glass stacked on one another, they dont reflect alot of light back (deffinatly not the way a Round does) and you can see right through them, and thats why that even with a VS you may still see inclusions where as a RB reflect the light back and causes the inclusions to get lost.

Hope this helps.

Anthony K

Exactly - that''s why I''m wondering if by VS2 when they say "inclusions visible at 10x" does that only apply to a RB or will it apply to cuts like asscher and EC etc?

 

[C Smith]

The ISG makes no distinction between cut when grading clarity. If I can see inclusions with my naked eye from the top, it is not a VS2 in my book . It's not even an SI-1.

 

[Anthony K]

OK.. So technically it applies to any shape diamond, however the visibility will depend on the way it is faceted. Now as far as types of inclusions go I would go ahead and read this to help better your understanding about the inclusions definitions and looks.

Hope this helps.

Anthony K

 

[Allium]

Visibility (what we call relief) is one of several factors considered in clarity grading. The way an inclusion reflects light is certainly going to influence the grade and it''s possible for a VS2 stone to have an eye visible inclusion but it''s pretty rare. Except of course in a step cut where eye visible would be the expected at VS2.

As for Sarin measurements, you can measure a diamond three different times and get three slightly different sets of measurements. There are limitations in every technology. However, keep in mind that you''re talking about very minute variations.

 

[Cehrabehra]

Date: 8/27/2006 7:51:56 PM
Author: Allium
Visibility (what we call relief) is one of several factors considered in clarity grading. The way an inclusion reflects light is certainly going to influence the grade and it''s possible for a VS2 stone to have an eye visible inclusion but it''s pretty rare. Except of course in a step cut where eye visible would be the expected at VS2.

As for Sarin measurements, you can measure a diamond three different times and get three slightly different sets of measurements. There are limitations in every technology. However, keep in mind that you''re talking about very minute variations.

Hi Allium thank you for your response... I probably should have stated that I''m specifically talking about an OMC... I didn''t mention it because I didn''t think many would know the answer to that but I figured it would be similar to an EC where clarity is concerned.

I''m not sure what you mean by "eye visible would be the expected at VS2". Does that mean that VS2 EC aren''t really eye clean or that standards for VS2 are a little tighter because of the faceting?

 

[Anthony K]

Date: 8/28/2006 1:48:22 AM
Author: Cehrabehra

Date: 8/27/2006 7:51:56 PM
Author: Allium
Visibility (what we call relief) is one of several factors considered in clarity grading. The way an inclusion reflects light is certainly going to influence the grade and it''s possible for a VS2 stone to have an eye visible inclusion but it''s pretty rare. Except of course in a step cut where eye visible would be the expected at VS2.

As for Sarin measurements, you can measure a diamond three different times and get three slightly different sets of measurements. There are limitations in every technology. However, keep in mind that you''re talking about very minute variations.

Hi Allium thank you for your response... I probably should have stated that I''m specifically talking about an OMC... I didn''t mention it because I didn''t think many would know the answer to that but I figured it would be similar to an EC where clarity is concerned.

I''m not sure what you mean by ''eye visible would be the expected at VS2''. Does that mean that VS2 EC aren''t really eye clean or that standards for VS2 are a little tighter because of the faceting? With an EC you will really have to see it in person to judge it, but a VS2 would generally be the starting point on "eye clean" EC diamond, where as a round would start with SI2. With a OMC you could do a little less clairity because it is not a step cut stone.
AK