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How are Si1 and Si2 graded? What makes them one grade vs the other?
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stepcutgirl
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Cinna
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Honestly do not know. But I asked my appraiser that about the difference from a VVS1 and a VVS2. My diamond had a microscopic dot only visible at the highest magnification his microscope would go (at 40x I believe.) When I asked him about it, he said that at a VVS1 instead of 2, it would be even harder to locate and even smaller than that.
So maybe it's the same deal. A bit of a judgement call from practice and training at how many inclusions versus how easy it is to spot the inclusions in a SI1 versus SI2 I'm thinking?
So maybe it's the same deal. A bit of a judgement call from practice and training at how many inclusions versus how easy it is to spot the inclusions in a SI1 versus SI2 I'm thinking?
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Clarity grading is done based on the presence of imperfection.
After looking at many diamonds of different grades, it''s possible to get a feel for how much imperfection should be SI1, and how much should be SI2.
It''s always a judgement call- but there''s a lot of consensus on the grades between GIA, and the trade at large.
Remember, the clarity is NOT graded based on visibility of imperfection- which means an SI2 might be eye clean, while an SI1 might not be.....
After looking at many diamonds of different grades, it''s possible to get a feel for how much imperfection should be SI1, and how much should be SI2.
It''s always a judgement call- but there''s a lot of consensus on the grades between GIA, and the trade at large.
Remember, the clarity is NOT graded based on visibility of imperfection- which means an SI2 might be eye clean, while an SI1 might not be.....
susimoo
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Wow, this befuddles me even more! How is that?
I thought that generally, the bigger and more visible the inclusions are, the lower down the clarity grade the stone will go. I understand also that the effect on structural integrity of the stone will come into play too (but that itself is dependent on the size and severity of the inclusions, or so I believe). So for example, a feather on a VS1 or VS2 diamond is usually so small (I know because my 3carater is a VS2 with a feather on the girdle so small that I and even jewellers have trouble locating, even with a loupe), whereas my Si2 diamond has a feather that can fairly easly be located with a loupe (but not with your unaided eyes).
Going back to my original Q of how to distinguish an Si1 versus an Si2, surely the larger and ugly the inclusions are, the more likely the stone in question is going to be graded an Si2 rather than Si1?? Having said that, my Si2 has twinning wisps (though long) cannot be seen with the naked eye and can only be located with a loupe in very good bright lighting. In fact, I've owned this stone for 2 years now and the first time I actually saw them with a loupe was a couple of weeks ago in a jeweller store with lots of very bright lighting. This stone also has some white/ clear crystals that are not eye-visible (can only be seen with a loupe).
On the other hand, I have an Si1 which although is eye-clean, has some so-called "clouds" which I understand is a collection of "pinpoints" which in fact look to me like black crystals. It's beginning to bug me, because they are black and can VERY easliy be located with a loupe. This cluster of pinpoints is large enough that IMHO (and novice opinon) should have been rendered an Si2 instead. What makes it worse is that these clouds or pinpoints are reflected throughout the diamond that when you look at it (again with a loupe), it looks like it has lots of black crystals.
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Oh also, my understanding is that the stone is correctly graded, which led me to ask this Q. I mean what yardsticks do the people at AGS or GIA use to determine if a stone is one grade and not another?
Not to labour the point but my Si2 I believe is truly an Si2 (due to the inclusions that it has, as well as their size). My Si1, I''m curiious as to how GIA came to their decision.
Not to labour the point but my Si2 I believe is truly an Si2 (due to the inclusions that it has, as well as their size). My Si1, I''m curiious as to how GIA came to their decision.
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You lucked out!
I'm curious too. What kind of inclusion(s) does your stone have and where is/are it/they located?
ETA: In my (novice) experience, VVS stones often only have pin-prick sized pinpoints that you cannot see with a loupe, only with a microscope. Also, the distinction between VS and VVS is more marked. I think the distinction between VVS1 and VVS2 is more akin to that between an Si1 and Si2, in that the inclusions seem so similar, how do you decide which is 1 and which is 2?
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Yes, actually I am. On the one hand, I think this is a mind-clean issue for me. On the other, I can't help but think that if I'd bought an Si2 stone, that grading would have settled in my mind and I wouldn't have pondered about the clarity issue (or rather more accurately about how it might bug me). As mentioned, I do have an Si2 stone and its clarity-grading, as well as the actual inclusions arising from that (or is it the other way round, LOL?!), have *never* once bothered me. I guess I just expected the Si1 to be a bit more ...oh I don't know...not so included.
I do believe that both the quantiy as well as the type/ nature of the inclusions that make the grading of a stone. But of course I am not a professional and don't know exactly how stones are graded, hence my original Q.
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Oh I see what you''re saying, silly me!
I agree with what you''re saying, hence my reasoning for questioning the clarity-grading of my Si1 stone. I think to be safe for *me*, from now on I''m going to think of Si1 and Si2 as one grade, and I''m going to think of them as "fairly included" - distinct from the VS group which is much cleaner in my mind. I don''t know if that makes sense to anyone else, LOL!
Stephan
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There are five factors weighed when assessing the clarity of a diamond:
1. Size of inclusions
2. Number of inclusions (this includes reflections visible through the crown at 10x magnification.)
3. Location of inclusions (center is worse, side is better)
4. Color/relief of inclusions (the more visible the worse, and the blacker the worse)
5. Nature of inclusions (if the flaw affects the durability of the diamond)
The first four of these are judged at 10x magnification, the nature can be judged at higher levels of magnification.
All of these factors are weighed and a grade is assigned. There are very few hard and fast rules to distinguish one grade from another, ultimately it is a judgement call. To get proficient (at least to the standards of a grading lab) you would need to see many thousands of diamonds. I hope this clairfies this at least a little.
Good luck.
1. Size of inclusions
2. Number of inclusions (this includes reflections visible through the crown at 10x magnification.)
3. Location of inclusions (center is worse, side is better)
4. Color/relief of inclusions (the more visible the worse, and the blacker the worse)
5. Nature of inclusions (if the flaw affects the durability of the diamond)
The first four of these are judged at 10x magnification, the nature can be judged at higher levels of magnification.
All of these factors are weighed and a grade is assigned. There are very few hard and fast rules to distinguish one grade from another, ultimately it is a judgement call. To get proficient (at least to the standards of a grading lab) you would need to see many thousands of diamonds. I hope this clairfies this at least a little.
Good luck.
That is an interesting question that I never really gave much thought. I can surely say that it is different for each stone. A step cut is likely to have fewer reflections than a brilliant because there are fewer facets for it to reflect from. But having a broad extinct facet behind a crystal can make it more obvious. So overall it is very hard to say. Sorry I cannot give a straight yes or no, but that''s gemology for you.
Good luck.
Good luck.
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