Round Diamond -- Cut v. Carat

[colgin]

I just wanted to say how wonderful and helpful this site is. In the past month I had educated myself quite a bit in terms of the very basics about diamonds but I feel like my knowledge has gone up exponentially since reading this site.

I am currently looking for a round diamond for an engagement ring for my girlfriend. To me cut is very important but size is the most important factor to my girlfriend (although she says that, of course, she does not want a dull stone). I am not sure how much she appreciates the difference between a truly good cut and an ordinary one. In any event, I had been trying to find something in the 2.5c range that both of us would be happy with.

My question relates to cut v. size. How much of a difference is there between an "ideal", "very good" and "good". Is the difference between "ideal" and "very good" noticeable? What about "very good" v. "good"? If my girlfriend wants size am I better off with just a "good" cut in the larger size. I would think I am better off with 2.25c in a "very good" or "ideal" if I can find it. For your reference I am looking for color of no worse than H (or perhaps I if it does not show) and clarity of no worse than VS2 (or perhaps SI1 if any imperfections are hidden). My price range is $20,000 give or take a little. Any thoughts or suggestions are greatly appreciated.

 

[valeria101]

Well... if you are asking about some scores of 2 and 3 on the HCA, than this is for Garry to explain.

It is not "size" that makes a diamond "ideal" but the proportions of the cut that make it as brilliant as possible. These proportions hardly affect weight or size (diameter).


The measures that most influence the size of a diamond (this is the diameter, not the weight) would be depth and then girdle thickness. Surely a stone with 55% depth will have a larger diameter than an AGS0 stone and but it wold not match it's brilliance either. Any deeper cut than the ideal range (say 64% or more) would have a smaller diameter.

A stone with very thick girdle but depth somewhere in the AGS0 interval, will have a smaller diameter than one with the same depth an a medium girdle. Around 2.5cts, this effect should show. If you look on the AGA cut charts, the top classes mention "medium to slightly thick" as max, for good reason.

It is true that diamonds with large tables are a bit havier than those with smaller tables, but the difference is not very significant. From this point of view, and "ideal cut" with 56% table would probably be somewhat lighter than a "near-ideal" stone with 60% table... Not sure you wnat to see what 45% table looks like... although I must have a picture somewhere

Some non-ideals would have larger diameter (and les depth) than the the AGS0 minimum (say, 57-58% total depth), but than it is still the crown and pavilion angles that dictate brilliance. There is a good reason though why the "ideal" range of depth is higher, you may find an explanation on THIS thread.

All in all, a stone of 59%-60% depth with a thin-medium girdle and the right combination of crown and pavilion angles would show the most of the 2.5 cts. I ( just my opinion, of course) would not get lower than 3 on the HCA, if "above 2" is not what you are after. However, premiums are charges on AGS0 and H&A pedigree, not the HCA. So you can definitely find a stone with good score and no add-in, either by asking for Sarin on a good "contender" or hunting down stones with HRD, IGI or EGL certs and the right proportions already listed on the cert.

If the "ideal cut" pedigree is not your focus, than you may want to skip the premium on H&A stones, not avoid considering proportions altogether

You don't have to agree, but it is one view on these things I found relevant - especially since H&A and "ideal proportiosn" are often used one for another, when they aren't the same, really.

Hope this helps...

 

[hoorray]

Garry posted a couple of pictures yesterday that I thought really showed the impact of cut to visual size. Check here. I personally would go down .25c in size and stay with an ideal cut.

Also, a quick search on the ps engine find a few that look interesting, particularly: stone 1, should still look very white -- the ACA's are supposed to be beautiful stones.

 

[valeria101]

(posting in the same time with Lop, I guess

)

Not that there is a ton of stones G-I, VS2-SI1, just below 2.5cts !

but there are a few, including ideals:

2.23 H-SI1, AGS cert, $20k at Abazias (AGS cert measn that the critical crown and pavilion angles are already available on the cert).

There were 10 "Ideal Cut" stones with the right specs and price listed at DirtCheapDiamonds of, which, this one was the largest (H-VS2, 2.38 cts, $20 350 Knowing that DCD selects diamonds for their proportions, it would be worth asking for the Sarin data on such a stone. The stones is their "Expert Selection" come with the proportiosn listed, but none matches your criteria at the moment...

And a no-excuse ideal cut ACA 2.52, I, VS2 (AGS0 and H&A), $20k at Whiteflash

 

[glitterata]

Does she want it to LOOK big, or does she want it to hit a particular carat weight so she can tell her friends it's (say) 2.5 carats?

If you care about how big it looks, make sure you pay attention to the diameter.

 

[valeria101]

All theory aside, it doesn't seem like you need to skimp cut quality with the resepctive budget in hand. And it would be a shame to end up with an odd-looking stone for the money... Not that non-ideals would be bad, just less predictable. 2.5 cts AGS0 seems perfectly feasible though.

Among the "ideal cut" diamonds at Blue Nile, there were 5 or 6 between 2.2 and 2.55 matching your criteria (including price). I do not know what BN defines as "ideal" but a few of these stones come with AGSL certificates - all AGS0 and a couple with top HCA scores to boot. The two below were the largest stones, but a 2.22cts G-SI was in the group too if color is a concern.

If some piece with GIA (not AGS) cert catches your eye, BN has provided Sarin data on their stones in the past, and they could do the same again, I suppose.

 

[colgin]

Thanks for your responses everyone. I had already listed the 2.52c stone on Whiteflash but will look up the other ones. Thanks again so much.

 

[solange]

I am very pleased with the stone I just bought from Whiteflash. Many of the vendors have access to stones that are not on their site or on the multiple listing service. New stones come on the market daily and may be sold before they are listed.
Lesley found me a perfectly eye clean SI2 I color that shows white from a manufacturer before it was listed.You can see my ring on Show me the RIng. I got a great ring for a great price with her guidance and the information I got from Brian, the ACA cutter.
You might consider calling some of the vendors on Pricescope to see if they have access to stones not listed or can advise you on stones they already have.

 

[hoorray]

One more thought on the size issue -- how you set it will impact how big it looks. I have a 2.52c. When we were shopping it didn't look that big loose, and in comparison, the 2.25s and 2.35s that we looked at looked small.

Once set it was a different story completely. It looked HUGE, and I realized that the 2.25s and 2.35s would have been just fine also. I've gotten used to, and love, the size, but I was wrong in thinking that the smaller stones were too small. THey would have looked great also. I have a solitare, semi-cathedral setting. It sits mediumly high, and I'm sure looks larger than if I had it in a very low setting.

Anyway...I'd be on the phone to Lesley at Whiteflash about that I/SI1. It looks like a beautiful stone on paper. GOod luck!

 

[searcher]

I just went through a similar problem. I went to stores with a budget and the weight of her sister-in-law's ring (stats unknown). It's not such a great way to go about this decision. You are putting a lot of thought into this. She is not the one staying up late reading pricescope and sneaking off to jewelry stores. Trust yourself, and buy from a place with a good return policy. My advice is to pick carat last, after you decide what quality you're comfortable with. No one will criticize you for buying what you can afford. By the way, I agree that this forum is really helpful. Thanks everybody!

About cut, I think symmetry has something to do with the grading systems, but that it's not visually significant. It's also my impression that the human eye is about as good as all the technology out there right now. All of these mathematical systems and so forth are attempting to predict a light pattern that is pleasing to your eyes. If a diamond looks good to you, looks good to a jeweler you trust, and has a reasonably good cut rating or proportions, then I wouldn't get too hung up on whether it's the top grade cut. Systems that grade cut are only meant to help you. If you're really worried, see if the store has a similar diamond with a perfect cut and place it side-by-side with your stone. It's more fun if you don't know which is which to start.

 

[hoorray]

----------------
On 6/1/2004 12:16:30 AM searcher wrote:


About cut, I think symmetry has something to do with the grading systems, but that it's not visually significant. It's also my impression that the human eye is about as good as all the technology out there right now. All of these mathematical systems and so forth are attempting to predict a light pattern that is pleasing to your eyes. If a diamond looks good to you, looks good to a jeweler you trust, and has a reasonably good cut rating or proportions, then I wouldn't get too hung up on whether it's the top grade cut. Systems that grade cut are only meant to help you. If you're really worried, see if the store has a similar diamond with a perfect cut and place it side-by-side with your stone. It's more fun if you don't know which is which to start.----------------

Agreed 100% with a caveat. Don't do this comparison under bright halogen store lighting. Find some real lighting to do any comparisons you are going to do. Store lighting is so bright that everything looks good.

Good luck!

 

[Dancing Fire]

one good thing about the store ligthing,if the stone you are looking at don't go BLING BLING !! you know its a pretty bad stone.