clarity question (and certification)

[searcher]

Should one automatically assume that a diamond with more visible inclusions also has more microscopic inclusions? How much will this affect light return? Or which is a more accurate statement:

A) An SI2 diamond returns 99% as much light as an IF diamond with the same proportions

*or*

B) An SI2 diamond returns 50% as much light as an IF diamond with the same proportions (due to light scattering after it hits hundreds of small inclusions)

I''ve found a nice SI2 that''s eye-clean to me, but I don''t trust my eyes to pick up sparkle, especially when other variables are thrown in (cut, color). If anyone wants to comment on the value of an EGL or AGA certification please chime in too. Has any research been done producing correlation coefficients between different labs vs. GIA?

thanks,
Jeff

 

[aljdewey]

Hi, Jeff: For the most part, clarity has NOTHING to do with sparkle. Your diamond would have to be horribly, horribly included before it actually affected light return.




If the SI2 is eyeclean, that's all you need to worry about.




Whether or not a diamond sparkles, and how much it sparkles, is strictly a function of its cut proportions. Find out the crown/pavilion angles for the stone, and that will tell you how it should be expected to perform.

 

[carina]

I don't understand, I have never seen an SI1 or 2 eye clean diamond.
Most of them are horrible and have white clouds, bubbles, black carbon, etc.
Why does this forum emphasize so much on an eye clean SI1 being ok. You would not be a very detailed skilled person if you didn't see the flaws that interfere with the brilliance on this grade diamond. There isn't anything like a clear clean diamond. I'm not nearly an expert but I would never buy an SI grade just from hands on real life observation. When you look at a diamond you want the squeaky clean clear glass look.

 

[moremoremore]

well, then you haven't see enough si1 and si2s. I've seen eye clean both. And some si2s were even better than the si1s! And I'm quite detailed and skilled, thank you!

 

[aljdewey]

Carina, how many AGS0, SI diamonds have you seen? I ask because if you're basing your comments on mall diamonds, I'd tend to agree that perhaps mall-grade SI diamonds don't always appear eyeclean.




However, well-cut diamonds tend to mask lower color and mask clarity, and if you haven't seen many of them, you may not know that.




I have seen several of them.....and when you go with better cut diamonds, it tends to mask the clarity. I own a completely eyeclean SI2 diamond. It has white, wispy inclusions and some pinpoint clouds. None of that is visible to the naked eye - not even in gazing through the size of the diamond. I've seen at least 15 eyeclean SI1 diamonds.....again, all well-cut stones.




This forum emphasizes eyeclean SI1s because most of the shoppers are considering extremely well-cut diamonds and can therefore afford to drop on clarity and save a bundle without any visual sacrifice to the naked eye.




Also, someone has misinformed you on clarity. Clarity doesn't interfere with brilliance.....clarity doesn't affect light performance *at all* except in the most extreme cases of horribly included stones. What affects a stone's brilliance/fire/scintillation is its cut proportions, not its clarity.

 

[pqcollectibles]

----------------
On 5/21/2004 9:59:38 AM carina wrote:

I don't understand, I have never seen an SI1 or 2 eye clean diamond.
Most of them are horrible and have white clouds, bubbles, black carbon, etc.
Why does this forum emphasize so much on an eye clean SI1 being ok. You would not be a very detailed skilled person if you didn't see the flaws that interfere with the brilliance on this grade diamond. There isn't anything like a clear clean diamond. I'm not nearly an expert but I would never buy an SI grade just from hands on real life observation. When you look at a diamond you want the squeaky clean clear glass look.----------------

If the SI Graded diamonds you've seen were Mall store diamonds, they may have really been I2 or higher in clarity,........... from the description you gave. I've seen I3 diamonds that were so included with white pinpoints they did not refract light. They were rather opalescent looking instead. Those diamonds are often affectionately referred to as "frozen spit".

I have seen SI diamonds with dark gemstone flecks in them that were visible from the side. Occassionally you will see an inclusion thru the top. Many accurately graded, well cut SI diamonds are totally eye clean even with close scrutiny.

 

[zeytoun]

If a bunch of tiny inclusions noticeably limit light return in a diamond, they would lower the clarity grade. I've graded a couple diamonds where there were VS2 feathers and many small inclusions that would each be VS1 clarity on their own, but when seen face up with the naked eye, made the stone look cloudy. The final verdict: I gave it an I1.

 

[Rhino]

For clarification...




In most SI graded diamonds the inclusions are not large enough to obstruct light return within the diamond assuming it was cut properly. However ... there are issues that can sometimes make even VS or VVS stones appear cloudy in certain light conditions due to irregularity within the crystal structure. Broke my heart to turn down a 1.96ct E VS1 due to that phenomena and also proves the point that paper alone doesn't tell the whole story. Physical exam by a pro is always recommended.

 

[valeria101]

Ouch! That much internal graining... makes quite a sight

Quite curious here... where were those SI's with "hundreds of small inclusions" thick enough to obstruct light?


I don't think you would find reliable stats on what's the precise expectation that a certain diamond graded by EGL would return that many grades different from GIA and so forth. That would be a heck of an expensive study given what the "sample" needs be. And then... how do you know where that one diamond you are interested in is right on trach with the average? Worse still, labs would not absolutely guarantee their greades for re-certification. GIA says that it's grades are robust to re-certification by GIA itself, up to half a grade: this is not 100% by all means. Is this bad? Not really... all in all price are not clear cut along grades either.

So... would an appraisal settle it for you?

O course there is no way to award "definitive grades" to a diamond. But a reasonable value based on as much grading accuracy as possible ? Sure so

 

[searcher]

thanks for your feedback! I think my new personal cut-off point where I can't see anything amiss is about a G, SI1, but I'm getting an F VS2 for extra piece of mind.