Ideal Cut or Round Brilliant

[sasa]

After reading the tutorial, I''m still confuse with the cut. If I want to buy a round diamond, do I go with ideal cut or round brilliant. how can you tell if a diamond is badly cut??

 

[Hest88]

I know it''s confusing the first time you read the tutorial, but now that you''ve had a first pass it''s a good idea to read it again when the vocabulary is no longer completely unfamiliar. A "round brilliant" is the shape of the diamond; it has nothing to do with how well it''s cut. Thus "ideal cut" and "RB" can be mutually exclusive. First you need to decide if you want a RB as a shape as opposed to a princess or a pear shape, etc., and then you want to focus on the best cut you can afford.

 

[DiamondExpert]

Round refers to the shape of the stone, and brilliant refers to the pattern of faceting. This pattern of faceting was originally designed to maximize brilliance and dispersion in diamonds.

A standard round brilliant (SRB) has 57/58 facets (1 table, 8 bezel facets, 8 star facets and 16 upper-girdle facets on the crown; and 8 pavilion facets, 16 lower-girdle facets, the 58th being a culet on the tip of the pavilion, if present.)

Many of the different shapes of diamonds tend to be brilliant cut. Notable exceptions are EC and Asschers, which are step cut.

In round stones, SRB's may or may not be Ideal cut depending on the definition of Ideal you use...many use the currently defined AGS0 grade for proportions, polish and symmetry to mean Ideal.

 

[sasa]

So a round shape diamond can be either ideal cut or round brilliant? The reason I asked is because couple days ago I was browsing thru a website and saw a round shape diamond I really like, in the cut description the vendor put round brilliant. And I remember reading in the forum that idal cut is the best cut for a diamond. I was just wondering which one is better?

 

[DiamondExpert]

Not exactly...the term Ideal, as defined by AGS for round stones, refers to a round brilliant cut, so round brilliant cuts can be non-ideal or ideal depending on the cut parameters.

In other words, the AGS-defined Ideal round brilliant cut diamond is a sub-set of all rouind brilliant cut diamonds.

To put it another way, all AGS-defined round Ideal cuts are round brilliant cuts, but not all round brilliant cuts are AGS-defined Ideals.

 

[sasa]

the vendor only put round brilliant as the description for the cut. Do I need to contact the vendor and ask if it''s ideal??

Thanks for all ur info DiamondExper

 

[DiamondExpert]

Yes, it may or may not be an ideal cut...and ask for either a copy of the Diamond Quality Document if it's AGS graded, or a grading report if it's GIA graded.

In the case of GIA grading you will also need a proportional analysis done with either a Sarin or OGI machine.

The other possibility is that it has no grading report, and if so, you also need to know this.

 

[Maxine]

More specifically, ask for the measurements....depth% table% and crown and pavillion angles....people have different "ideas" of what constitutes "ideal" when they are trying to sell you a stone....In the whiteflash expert selection, they have round brilliant stones and round ideal cut stones....(which may be very nice, but not exactly cut to ideal proportions)....If you look at the ideal scope images of each, they look different...Whiteflash (and other reputable vendors) do not misprepesent the cut of their stones.....If they are not ideal cut they will tell you....and they still might be a very nice stone that you might like (often the price is lower compared to similarly sized ideal-cut stones). Have you read the educational tutorials here or on other sites??? Good old gold have an extensive educational tutorial, also.....

 

[lostdog]

Basic shape = Round

Round shape with the standard 57 or 58 facets = Round Brilliant

Round Brilliant with facets arranged within specific angles and proportion ranges = Ideal Cut

But Ideal Cut is not a single standard. Exactly what that inter-relationship is, with the angles and proportions of the facets is in relation to certain "Ideal" standards, that becomes the issue.

Ideal Cut in the description could mean:
Standards for AGS Cut Grade 0
Standards for AGA 1A or 1B
Vendor defined standards (Blue Nile, for example)
Tolkowsky Ideal Cut parameters (the classic)
Holloway Cut Advisor BIC (Brilliant Ideal Cut) or FIC (Fiery Ideal Cut) parameters
(and many others)

(but there's nothing to stop an agressive retailer from throwing around the "Ideal" term when the stone only meets ideal on 1 or 2 measurements. Thay love to do this to you with stones that don't have detailed information available, just simple depth and table percentages, if that. You have to know the standards being used for Ideal to have any meaning.)

And remember that under the current system, soon to change, that the Cut AGS 0 ideal by itself doesn't gurantee best visual performance. That's where it gets interesting. HCA score is one method of dealing with the issue.

And aside from Ideal, there is H&A which may occur on either Ideal or Non-Ideal Cut stones. But where Ideal is at least supposed to be in relation to some defined numbers, H&A is a subjective call, like eye-clean is. You need to know the vendor's individual criteria for the term and then understand it enough so that you know what it means as far as what see with your own eyes, if you want to be sure. Angles and proportions are on an AGS cert, but not H&A appearance.

(And this is just Cut, there are the other Polish/Symmetry grades, too, that can be Ideal on some AGS certs. And there is more to symmetry than simply what's on the cert as Ideal or not.)

So, B, hopefully this helps a little. You'll probably have to read those tutorials a few more times in a few more places to let it really start to make sense.

No one general term yet makes it 100% clear what quality of cut you are getting (not talking branded cuts here, just market-wide terms). And the task is complicated because visual performance is actually an umbrella term for several different interactions of light, mineral, and eyes. You can't just define it as reflected light or sparkliness. And for real world beauty, there's a range of lighting conditions to perform under, not just the direct overhead specular stuff that retailers never go without.

So you ultimately have to analyze in regard to several issues and Ideal is only a guidepost, not a guarantee.

Not sure if you've been through just PS's info or elsewhere, but if not then good stuff to cover would be the Whiteflash material on H&A, Good Old Gold's cut lessons, the HCA explanations, and the Idealscope explanations.

 

[sasa]

Thank you lostdog for the clear explanation

 

[lostdog]

You're welcome. The posts leading up to it covered many of the points, but I thought to give it a shot tying it together.

The thing not emphasized is that Ideal or AGS0 or HCA or whatever you are using is a tool to narrow down your search, not something to accept blindly. Looking at enough diamonds, physically looking a them in person, unaided and with a loupe and in varying lighting, will give you enough experience to tell when the stone in question is truly something worth getting or just technical satisfaction that earns a label. Ideal and Beautiful are two different things.

 

[icemyster]

Date: 5/6/2005 3:47:27 AM
Author: lostdog
Basic shape = Round



(but there''s nothing to stop an agressive retailer from throwing around the ''Ideal'' term when the stone only meets ideal on 1 or 2 measurements. Thay love to do this to you with stones that don''t have detailed information available, just simple depth and table percentages, if that. You have to know the standards being used for Ideal to have any meaning.)

How ture....I have heard this many times...great words of wisdom.